magnetic recording media

Abstract

The main purpose of the present invention is to provide a high-recording-density magnetic recording medium capable of preventing an increase in frictional force even in a situation where the recording medium is driven many times. Furthermore, in addition to said prevention of an increase in frictional force, another purpose of the present technique is to maintain a polishing force when the recording medium is driven many times. The present technique provides a magnetic recording medium having a magnetic layer containing magnetic powder, wherein: the magnetic layer contains electrically conductive first particles and second particles having a Mohs hardness of 7 or higher; protrusions are formed on a magnetic layer-side surface by the first particles and the second particles; and protrusions formed by the second particles have an average height (H2) of 7 nm or less, contain an aliphatic acid, and have an aliphatic acid extraction ratio of 45% or higher as defined by the expression given below.　Aliphatic acid extraction ratio (%) = [amount of aliphatic acid extracted in five minutes (mg / m2) / total amount of extracted aliphatic acid (mg / m2)] x 100

Description

[Technical Field]

[0001] The present technology relates to magnetic recording media. [Background technology]

[0002] With the development of IoT, big data, and artificial intelligence, the amount of data collected and stored is increasing dramatically. Magnetic recording media are often used as a medium for recording large amounts of data.

[0003] Various technologies have been proposed for magnetic recording media. For example, Patent Document 1 listed below describes a tape having a multi-layer structure including at least a magnetic layer, the total thickness of the tape being 5.6 μm or less, a plurality of recesses being arranged on the surface of the magnetic layer, the value obtained by dividing the depth D1 of the recesses by the thickness D2 of the magnetic layer being 15% or more, the magnetic layer being perpendicularly oriented, the degree of perpendicular orientation under the condition without demagnetizing field correction being 65% or more, and a plurality of recesses being formed in the magnetic layer, each recess being 20% ​​or more of the thickness of the magnetic layer, and the number of the recesses being 6,400 μm or more of the magnetic layer. 2 55 or more per surface area of ​​magnetic recording tape is disclosed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 159465 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, magnetic tape (magnetic recording media) has come to be used for archiving purposes in data centers. Accordingly, the demand for reliability of magnetic tape has also increased. It is particularly important that magnetic tape can run stably even after multiple runs.

[0006] Furthermore, while data tracks are becoming narrower as magnetic tape capacity increases, it is undesirable for servo signals to be read incorrectly.The increase in frictional force on the magnetic tape caused by multiple runs of the magnetic tape can lead to errors in reading the servo signals, which is undesirable for magnetic recording.

[0007] Furthermore, if the frictional force of the magnetic tape is high, a stick-slip phenomenon may occur. This phenomenon may result in deviations in the running speed of the magnetic tape. Furthermore, if the frictional force is high, the tape may also move when the magnetic head is moved laterally to correct the servo position, which may prevent immediate correction of the servo position.

[0008] Furthermore, it is necessary to improve the abrasive power of the magnetic tape, for example, to clean off deposits on the magnetic head. Running the magnetic tape multiple times can also cause a decrease in the abrasive power of the magnetic tape against the magnetic head.

[0009] To prevent the increase in frictional force during magnetic tape running, it is conceivable to use, for example, a solid lubricant component (such as carbon particles that act as a solid lubricant). Also, for magnetic head cleaning, it is conceivable to use a component with an abrasive effect (and even an anchoring effect) (such as particles with a high Mohs hardness, particularly alumina). It is conceivable that a combination of these two components can be included in the magnetic tape (e.g., the magnetic layer) to prevent the increase in frictional force and clean the magnetic head. However, if the abrasive power becomes too high, the magnetic head itself may be damaged, or the heat and charge generated by friction may increase, causing greater damage to the magnetic head.

[0010] The primary objective of this technology is to provide a magnetic recording medium with high recording density that can prevent an increase in frictional force even after multiple runs. A further objective of this technology is to provide a magnetic recording medium that, in addition to preventing the increase in frictional force, can maintain abrasive power during multiple runs and efficiently expose fatty acids and fatty acid esters to the surface, thereby mitigating damage to the magnetic head. [Means for solving the problem]

[0011] The present technology has a magnetic layer containing magnetic powder, the magnetic layer contains first particles having electrical conductivity and second particles having a Mohs hardness of 7 or more, protrusions are formed on the surface of the magnetic layer side by the first particles and the second particles, The magnetic recording medium has protrusions formed by the second particles with an average height (H2) of 7 nm or less, contains fatty acid, and has an extractability of fatty acid defined by the following formula of 45% or more. Extraction rate of fatty acids (%) = [5-minute extraction amount of fatty acids (mg / m 2 ) / Total fatty acid extraction amount (mg / m 2 )] x 100 5-minute extraction amount of fatty acids (mg / m 2 ) is 3.0 mg / m 2 It could be more than that. Total fatty acid extraction (mg / m 2 ) is 5.0 mg / m 2 It could be more than that. The fatty acid may be stearic acid. The magnetic recording medium may further contain a fatty acid ester, and the extraction rate of the fatty acid ester defined by the following formula may be 60% or more. Extraction rate of fatty acid ester (%) = [5-minute extraction amount of fatty acid ester (mg / m 2 ) / Total fatty acid ester extract (mg / m 2 )] x 100 5-minute extraction amount of fatty acid esters (mg / m 2 ) is 10.0 mg / m 2 It could be more than that. Total fatty acid ester extractables (mg / m 2 ) is 12.0 mg / m 2 It could be more than that. The fatty acid ester may be butyl stearate. The magnetic layer may have an average thickness of 0.08 μm or less. The magnetic recording medium may further include a non-magnetic layer. The non-magnetic layer may have an average thickness of 1.2 μm or less. The average thickness (average total thickness) can be 5.7 μm or less. The surface of the magnetic powder may be coated with a coating agent. The coating agent can be an organic acid. The second particles may be inorganic particles. The second particles may be alumina particles. The present technology provides a magnetic recording cartridge in which the magnetic recording medium is housed in a case while being wound around a reel. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing the configuration of a magnetic recording medium according to a first embodiment. [Figure 2] FIG. 1 is a schematic diagram showing the configuration of a recording / reproducing device. [Figure 3] FIG. 10 is a cross-sectional view showing the configuration of a magnetic recording medium according to a modified example. [Figure 4] FIG. 2 is an exploded perspective view showing an example of the configuration of a magnetic recording cartridge. [Figure 5] FIG. 2 is a block diagram showing an example of the configuration of a cartridge memory. [Figure 6] FIG. 10 is an exploded perspective view showing an example of the configuration of a modified magnetic recording cartridge. [Figure 7] 1 is an image showing an example of a surface shape imaged by an AFM. [Figure 8] FIG. 10 is a diagram showing an example of a protrusion analysis result obtained by AFM. [Figure 9] FIG. 10 is a diagram showing an example of a protrusion height distribution measured by AFM. [Figure 10] This is an example of an FE-SEM image. [Figure 11] This is a composite image created by overlaying an AFM image and an FE-SEM image. [Figure 12] This is an enlarged view of a composite image obtained by superimposing an AFM image and an FE-SEM image. [Figure 13] FIG. 13 is a diagram showing an example of the results of an AFM analysis of Line 1 in FIG. 12. [Figure 14] FIG. 10 is a diagram showing a cumulative frequency distribution of the height of protrusions formed by secondary particles (alumina particles). [Figure 15] FIG. 2 is a diagram showing an example of the shape of a particle of magnetic powder. [Figure 16] 1 is an example of a TEM photograph of a cross section of a sample. [Figure 17] 10 is another example of a TEM photograph of a cross section of a sample. [Figure 18] FIG. 1 is a diagram showing an example of a sample mount used for measuring the extraction rate of a fatty acid or a fatty acid ester. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments for carrying out the present technology will be described below. Note that the embodiments described below are representative embodiments of the present technology, and the scope of the present technology is not limited to these embodiments.

[0014] This technology will be described in the following order. 1. Description of this technology 2. First embodiment (1) Structure of magnetic recording medium (2) Explanation of each layer (3) Physical properties and structure (4) Manufacturing method of magnetic recording medium (5) Recording and playback device (6) Variations 3. Second embodiment (cartridge) (1) One embodiment of a magnetic recording cartridge (2) Modified magnetic recording cartridge 4. Working Example

[0015] In this specification, unless a measurement environment is specifically stated in the description of the measurement method, the measurement is performed in an environment of 25°C ± 2°C and 50% RH ± 5% RH.

[0016] 1. Description of this technology

[0017] The inventors have discovered that an increase in frictional force can be prevented by adjusting the extraction rate of the fatty acid or fatty acid ester contained in the magnetic recording medium as a lubricant, as described below, and by adjusting the height of the protrusions formed by the second particles.

[0018] That is, the magnetic recording medium according to the present technology has a magnetic layer containing magnetic powder, and the magnetic layer contains first particles having electrical conductivity and second particles having a Mohs hardness of 7 or more. The first particles are electrically conductive and can function as a solid lubricant. The second particles have a Mohs hardness of 7 or more, preferably 9 or more, and can have abrasive and anchoring effects. The first particles and the second particles form protrusions on the surface facing the magnetic layer. A method for measuring the average height (H2) of the protrusions of the second particles will be described below in 2.(3).

[0019] In the magnetic recording medium according to the present technology, the average height (H2) of the protrusions formed by the second particles may be 7 nm or less, preferably 6.5 nm or less, more preferably 6.0 nm or less, even more preferably 5.5 nm or less, and even more preferably 5.3 nm or less. When the magnetic recording medium has an average height (H2) of the protrusions formed by the second particles within the above numerical range, friction increase due to multiple runs is reduced, contributing to the ability to properly maintain the abrasive force against the magnetic head.

[0020] Furthermore, the lower limit of the average height (H2) of the protrusions formed by the secondary particles is not particularly limited, but may be, for example, preferably 2.0 nm or more, more preferably 2.5 nm or more, and even more preferably 3.0 nm or more.

[0021] As the magnetic recording medium runs, deposits adhere to the magnetic head. In order to remove such deposits from the magnetic head, the height of the protrusions formed by the second particles can be adjusted as described above, thereby improving the cleaning (polishing) power of the magnetic head. However, if the cleaning (polishing) power of the magnetic head is improved, the magnetic head itself may be polished and damaged, potentially resulting in a decrease in output.

[0022] The magnetic recording medium according to the present technology contains a fatty acid. The magnetic recording medium according to the present technology may further contain a fatty acid ester. Such a fatty acid or fatty acid ester seeps onto the surface of the magnetic recording medium, coating the surfaces of the second particles with the fatty acid or fatty acid ester, thereby reducing damage to the magnetic head.

[0023] The fatty acid or fatty acid ester is contained in the non-magnetic layer (underlayer) and the magnetic layer. Usually, the fatty acid is trapped in the magnetic or non-magnetic powder and hardly seeps out onto the surface of the magnetic recording medium.

[0024] In this technology, the extraction rate of the fatty acid or fatty acid ester is used as an index of the ease with which the fatty acid or fatty acid ester will leach out from the surface of the magnetic recording medium. That is, a high extraction rate value means that the fatty acid or fatty acid ester is not captured to a large extent by the magnetic powder or the like, and therefore leach out easily, while a low extraction rate value means that the fatty acid or fatty acid ester is captured to a large extent by the magnetic powder or the like, and therefore leach out less easily.

[0025] In the present technology, for example, the following method may be adopted to improve the extraction rate of fatty acids or fatty acid esters. (1) A method of suppressing the capture of fatty acids on magnetic or non-magnetic powders by using a coating agent (i) A method of coating the surface of a magnetic or non-magnetic powder using an organic acid having one or more polar groups such as carboxylic acid, phosphonic acid, or sulfonic acid, or a metal salt thereof that functions as an acid group, as a coating agent. (ii) A method of coating the surface of a magnetic or non-magnetic powder using a coupling agent (silane, aluminum, titanium, etc.) as a coating agent. (iii) A method in which carbon, metal oxides, or hydroxides (aluminum, yttrium, etc.) are used as a coating agent and adhered to the surface of magnetic or non-magnetic powder to reduce surface activity. (2) Changing the film structure, such as the thickness of the magnetic layer, the thickness of the non-magnetic layer, or the gap, to make it easier for the fatty acid ester to bleed. A method of adjusting the thickness of the magnetic layer, the thickness of the non-magnetic layer, the amount of hardener, the calendering conditions (temperature, pressure, etc.), and the amount of binder in the non-magnetic layer (P / B ratio).

[0026] In this technology, the extraction rate of fatty acids defined by the following formula can be 45% or more, preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more. If the extraction rate of fatty acids is less than 45%, friction increases, and the magnetic head deteriorates due to frictional heat and electrification. In addition, damage to the coating increases, powder fall increases, and durability deteriorates. Extraction rate of fatty acids (%) = [5-minute extraction amount of fatty acids (mg / m 2 ) / Total fatty acid extraction amount (mg / m 2 )] x 100

[0027] The upper limit of the fatty acid extraction rate is not particularly limited, but from the viewpoint of preventing the coating film itself from plasticizing, increasing powder shedding, and deteriorating durability, it is preferably 75% or less, more preferably 73% or less, and even more preferably 70% or less. The method for measuring the fatty acid extraction rate will be explained in 2.(3) below.

[0028] In addition, the 5-minute extractable amount of the fatty acid (mg / m 2 ) is preferably 3.0 mg / m 2 or more, more preferably 3.5 mg / m 2 or more, more preferably 4.0 mg / m 2 or more, and even more preferably 4.5 mg / m 2 It could be more than that.

[0029] The upper limit of the amount of fatty acids extracted in 5 minutes is not particularly limited, but is preferably 14.0 mg / m 2 or less, more preferably 13.0 mg / m 2 or less, more preferably 12.0 mg / m 2 or less, and even more preferably 10.0 mg / m 2 The method for measuring the 5-minute extractable amount of fatty acids is described below in 2.(3).

[0030] In addition, the total amount of fatty acid extracted (mg / m 2 ) is preferably 5.0 mg / m 2 or more, more preferably 7.0 mg / m 2 or more, more preferably 9.0 mg / m 2 or more, and even more preferably 10.0 mg / m 2 It could be more than that.

[0031] The upper limit of the total amount of fatty acids extracted is not particularly limited, but is preferably 16.0 mg / m 2 or less, more preferably 15.0 mg / m 2 or less, more preferably 14.0 mg / m 2 or less, and even more preferably 13.0 mg / m 2 The method for measuring the total amount of fatty acid extracted is described below in 2.(3).

[0032] The magnetic recording medium according to the present technology further contains a fatty acid ester, and from the viewpoint of suppressing increased friction, deterioration of the magnetic head due to frictional heat and electrification, increased damage to the coating film, increased powder fall-off, and further deterioration of durability, the extraction rate of the fatty acid ester defined by the following formula can be preferably 60% or more, more preferably 65% ​​or more, even more preferably 70% or more, and even more preferably 75% or more. Extraction rate of fatty acid ester (%) = [5-minute extraction amount of fatty acid ester (mg / m 2 ) / Total fatty acid ester extract (mg / m 2 )] x 100

[0033] The upper limit of the extraction rate of the fatty acid ester is not particularly limited, but from the viewpoint of preventing the coating film itself from plasticizing, increasing powder shedding, and deteriorating durability, it is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less. The method for measuring the extraction rate of the fatty acid ester will be explained below in 2.(3).

[0034] In addition, the 5-minute extractable amount (mg / m 2 ) is preferably 10.0 mg / m 2 or more, more preferably 12.0 mg / m 2 or more, more preferably 14.0 mg / m 2 or more, and even more preferably 16.0 mg / m 2 It could be more than that.

[0035] The upper limit of the amount of fatty acid ester extracted in 5 minutes is not particularly limited, but is preferably 25.0 mg / m 2 If the concentration exceeds 20.0 mg / m, plasticization of the coating film will progress and powder shedding may worsen. 2 or less, more preferably 19.0 mg / m 2 or less, more preferably 18.0 mg / m 2 or less, and even more preferably 17.0 mg / m 2 The method for measuring the 5-minute extractable amount of fatty acid esters will be explained in 2.(3) below.

[0036] In addition, the total amount of fatty acid ester extracted (mg / m 2 ) is preferably 12.0 mg / m 2 or more, more preferably 14.0 mg / m 2 or more, more preferably 16.0 mg / m 2 or more, and even more preferably 19.0 mg / m 2 It could be more than that.

[0037] The upper limit of the total amount of fatty acid esters extracted is not particularly limited, but is preferably 25.0 mg / m 2 or less, more preferably 24.0 mg / m 2or less, more preferably 23.0 mg / m 2 or less, and even more preferably 22.0 mg / m 2 The method for measuring the total amount of extracted fatty acid esters will be explained in 2.(3) below.

[0038] The magnetic recording medium according to the present technology is preferably a long magnetic recording medium, and may be, for example, a magnetic recording tape (particularly a long magnetic recording tape).

[0039] A magnetic recording medium according to the present technology may include a magnetic layer, a non-magnetic layer (underlayer), a base layer, and a back layer in this order, and may also include other layers in addition to these layers. The other layers may be selected appropriately depending on the type of magnetic recording medium. The magnetic recording medium is a coating-type magnetic recording medium. For layers included in the magnetic recording medium other than the above four layers, please refer to the descriptions thereof.

[0040] The average thickness (average total thickness) of the magnetic recording medium according to the present technology is t T may be, for example, preferably 5.7 μm or less, 5.6 μm or less, 5.5 μm or less, 5.4 μm or less, 5.3 μm or less, more preferably 5.2 μm or less, 5.0 μm or less, even more preferably 4.6 μm or less, and even more preferably 4.4 μm or less. Because the magnetic recording medium is so thin, for example, the length of tape wound into one magnetic recording cartridge can be made longer, thereby increasing the recording capacity per magnetic recording cartridge. The average thickness (average total thickness) t of the magnetic recording medium T The lower limit of t is not particularly limited, but for example, 3.5 μm≦t T is.

[0041] The average thickness t of the magnetic layer of the magnetic recording medium according to the present technology m The average thickness t of the magnetic layer is preferably 0.08 μm or less, more preferably 0.07 μm or less, even more preferably 0.06 μm or less, 0.05 μm or less, and even more preferably 0.04 μm or less. mAlthough there are no particular restrictions on the lower limit, it is preferably 0.03 μm or more. The method for measuring the average thickness of the magnetic layer will be explained below in 2.(3).

[0042] The average thickness of the nonmagnetic layer (average thickness of the underlayer) of the magnetic recording medium according to the present technology is preferably 1.2 μm or less, more preferably 1.0 μm or less, 0.9 μm or less, 0.8 μm or less, or 0.7 μm or less, and even more preferably 0.6 μm or less. The lower limit of the average thickness of the nonmagnetic layer is not particularly limited, but is preferably 0.2 μm or more, more preferably 0.3 μm or more. The method for measuring the average thickness of the nonmagnetic layer will be described below in 2.(3).

[0043] The average thickness of the base layer of the magnetic recording medium according to the present technology can be preferably 4.5 μm or less, more preferably 4.2 μm or less, 4.0 μm or less, 3.6 μm or less, and even more preferably 3.0 μm or less. The method for measuring the average thickness of the base layer will be explained in 2.(3) below.

[0044] The average thickness of the back layer of the magnetic recording medium according to the present technology is preferably 0.6 μm or less, more preferably 0.5 μm or less, and even more preferably 0.4 μm or less, 0.3 μm or less, or 0.25 μm or less. The method for measuring the average thickness of the back layer will be explained in 2.(3) below.

[0045] The average particle volume of the magnetic powder contained in the magnetic recording medium of this technology is 2600 nm 3 less than 2000 nm, preferably 3 or less, and more preferably 1600 nm 3 or less. By having the average particle volume within the above numerical range, the electromagnetic conversion characteristics are improved. Despite the fact that the average particle volume of the magnetic powder contained in the magnetic recording medium of the present technology is very small, the magnetic recording medium of the present technology has excellent thermal stability as described above. While it is difficult to achieve both electromagnetic conversion characteristics and thermal stability, the present technology can improve both. The average particle volume of the magnetic powder is, for example, 500 nm 3 Above 700nm, especially 3The method for measuring the average particle volume of the magnetic powder will be explained below in 2.(3).

[0046] In the present technology, the squareness ratio in the perpendicular direction can be preferably 65% ​​or more, more preferably 67% or more, and even more preferably 70% or more. By having the squareness ratio within the above numerical range, the perpendicular orientation of the magnetic powder is sufficiently high, resulting in a superior cNR. Therefore, superior electromagnetic conversion characteristics can be obtained. The method for measuring the squareness ratio in the perpendicular direction will be described below in 2.(3).

[0047] A magnetic recording medium according to the present technology may have, for example, at least one data band and at least two servo bands. The number of data bands may be, for example, 2 to 10, particularly 3 to 6, and more particularly 4 or 5. The number of servo bands may be, for example, 3 to 11, particularly 4 to 7, and more particularly 5 or 6. These servo bands and data bands may be arranged, for example, so as to extend in the longitudinal direction of a long magnetic recording medium (particularly a magnetic recording tape), particularly so as to be substantially parallel. The data band and the servo band may be provided on the magnetic layer. An example of a magnetic recording medium having such a data band and servo band is a magnetic recording tape conforming to the LTO (Linear Tape-Open) standard. That is, the magnetic recording medium according to the present technology may be a magnetic recording tape conforming to the LTO standard. For example, the magnetic recording medium according to the present technology may be a magnetic recording tape conforming to the LTO8 standard or later (e.g., LTO9, LTO10, LTO11, or LTO12). The width of a long magnetic recording medium (particularly a magnetic recording tape) according to the present technology can be, for example, 5 mm to 30 mm, particularly 7 mm to 25 mm, more particularly 10 mm to 20 mm, and even more particularly 11 mm to 19 mm. The length of a long magnetic recording medium (particularly a magnetic recording tape) can be, for example, 500 m to 1500 m. For example, a tape conforming to the LTO8 standard has a width of 12.65 mm and a length of 960 m.

[0048] 2. First embodiment

[0049] (1) Structure of magnetic recording medium First, the configuration of a magnetic recording medium 10 according to the first embodiment will be described with reference to Fig. 1. The magnetic recording medium 10 is, for example, a magnetic recording medium that has been subjected to a perpendicular orientation process, and as shown in Fig. 1, includes a long base layer (also referred to as a substrate) 11, a non-magnetic layer (also referred to as an underlayer) 12 provided on one major surface of the base layer 11, a magnetic layer (also referred to as a recording layer) 13 provided on the non-magnetic layer 12, and a back layer 14 provided on the other major surface of the base layer 11. Hereinafter, of the two major surfaces of the magnetic recording medium 10, the surface on which the magnetic layer 13 is provided will be referred to as the magnetic surface, and the surface opposite to the magnetic surface (the surface on which the back layer 14 is provided) will be referred to as the back surface.

[0050] The magnetic recording medium 10 has an elongated shape and runs in the longitudinal direction during recording and reproduction. The magnetic recording medium 10 may be configured to record signals at a minimum recording wavelength of preferably 100 nm or less, more preferably 75 nm or less, even more preferably 60 nm or less, and particularly preferably 50 nm or less, and may be used, for example, in a recording and reproduction device whose minimum recording wavelength is within the above range. This recording and reproduction device may be equipped with a ring-type head as a recording head. The recording track width is, for example, 2 μm or less.

[0051] (2) Explanation of each layer

[0052] (base layer)

[0053] The base layer 11 can function as a support for the magnetic recording medium 10 and can be, for example, a flexible, long, non-magnetic substrate, particularly a non-magnetic film. The average thickness of the base layer 11 is, for example, preferably 4.5 μm or less, more preferably 4.2 μm or less, and can be 4.0 μm or less, 3.6 μm or less, and even more preferably 3.0 μm or less. The lower limit of the average thickness of the base layer 11 can be determined, for example, from the viewpoint of film production limitations or the function of the base layer 11. The base layer 11 can contain, for example, at least one of polyester resins, polyolefin resins, cellulose derivatives, vinyl resins, aromatic polyether ketone resins, and other polymer resins. When the base layer 11 contains two or more of the above materials, the two or more materials may be mixed, copolymerized, or laminated.

[0054] The polyester resin may be, for example, one or a mixture of two or more of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PBT (polybutylene terephthalate), PBN (polybutylene naphthalate), PCT (polycyclohexylene dimethylene terephthalate), PEB (polyethylene-p-oxybenzoate), and polyethylene bisphenoxycarboxylate. According to a preferred embodiment of the present technology, the base layer 11 may be formed from PET or PEN.

[0055] The polyolefin resin may be, for example, one or a mixture of two or more of PE (polyethylene) and PP (polypropylene).

[0056] The cellulose derivative may be, for example, one or a mixture of two or more of cellulose diacetate, cellulose triacetate, CAB (cellulose acetate butyrate), and CAP (cellulose acetate propionate).

[0057] The vinyl resin may be, for example, one or a mixture of two or more of PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride).

[0058] The aromatic polyetherketone resin may be, for example, one or a mixture of two or more of PEK (polyetherketone), PEEK (polyetheretherketone), PEKK (polyetherketoneketone), and PEEKK (polyetheretherketoneketone). According to a preferred embodiment of the present technology, the base layer 11 may be formed from PEEK.

[0059] The other polymer resin may be, for example, one or a mixture of two or more of PA (polyamide, nylon), aromatic PA (aromatic polyamide, aramid), PI (polyimide), aromatic PI (aromatic polyimide), PAI (polyamideimide), aromatic PAI (aromatic polyamideimide), PBO (polybenzoxazole, such as Zylon (registered trademark), polyether, polyetherester, PES (polyethersulfone), PEI (polyetherimide), PSF (polysulfone), PPS (polyphenylene sulfide), PC (polycarbonate), PAR (polyarylate), and PU (polyurethane).

[0060] (magnetic layer)

[0061] The magnetic layer 13 may be, for example, a perpendicular recording layer. The magnetic layer 13 contains magnetic powder. In addition to the magnetic powder, the magnetic layer 13 contains first particles having electrical conductivity and second particles having a Mohs hardness of 7 or more. The magnetic layer 13 may also contain, for example, a binder. The magnetic layer 13 may also contain additives such as a lubricant and a rust inhibitor, as necessary.

[0062] The average thickness t of the magnetic layer 13 m The average thickness t of the magnetic layer 13 is preferably 0.08 μm or less, more preferably 0.07 μm or less, and even more preferably 0.06 μm or less, 0.05 μm or less, or 0.04 μm or less. mThe lower limit of the average thickness t of the magnetic layer 13 is not particularly limited, but is preferably 0.03 μm or more. m Being within the above range contributes to improving the electromagnetic conversion characteristics.

[0063] The magnetic layer 13 is preferably a magnetic layer that is perpendicularly oriented. In this specification, perpendicular orientation means that the squareness ratio S1 measured in the longitudinal direction (travel direction) of the magnetic recording medium 10 is 35% or less. The magnetic layer 13 may be an in-plane oriented (longitudinal oriented) magnetic layer. That is, the magnetic recording medium 10 may be a horizontal recording type magnetic recording medium. However, from the viewpoint of achieving high recording density, a perpendicular orientation is more preferable.

[0064] (magnetic powder)

[0065] Examples of magnetic particles constituting the magnetic powder contained in the magnetic layer 13 include, but are not limited to, epsilon iron oxide (ε iron oxide), gamma hematite, magnetite, chromium dioxide, cobalt-coated iron oxide, hexagonal ferrite, barium ferrite (BaFe), Co ferrite, strontium ferrite, and metals. The magnetic powder may be one of these, or a combination of two or more of these. Particularly preferably, the magnetic powder may contain ε iron oxide magnetic powder, barium ferrite magnetic powder, cobalt ferrite magnetic powder, or strontium ferrite magnetic powder. The ε iron oxide may contain Ga and / or Al. These magnetic particles may be appropriately selected by those skilled in the art based on factors such as the manufacturing method of the magnetic layer 13, the tape specifications, and the tape functions.

[0066] The average particle size (average maximum particle size) D of the magnetic powder can be preferably 22 nm or less, more preferably 8 nm or more and 22 nm or less, and even more preferably 10 nm or more and 20 nm or less.

[0067] The average particle size D of the magnetic powder is determined as follows. First, the magnetic recording medium 10 to be measured is processed by a FIB (Focused Ion Beam) method or the like to prepare a thin section, and the cross section of the thin section is observed by a TEM. Next, 500 ε-iron oxide particles are randomly selected from the TEM photograph, and the maximum particle size d of each particle is measured. max Measure the maximum particle size d of the magnetic powder. max The particle size distribution is calculated as follows: max " refers to the so-called maximum Feret diameter, specifically the maximum distance between two parallel lines drawn from any angle so as to be tangent to the contour of the ε-iron oxide particle. Then, the maximum particle size d max The maximum particle size d from the particle size distribution max The median diameter (50% diameter, D50) is determined and used as the average particle size (average maximum particle size) D of the magnetic powder.

[0068] The shape of the magnetic powder is preferably at least one of plate-like, spherical, and rectangular. The shape of the magnetic powder depends on the crystal structure of the magnetic particles. Examples of plate-like magnetic powder include BaFe and strontium ferrite, which have a hexagonal plate-like shape. Examples of spherical magnetic powder include ε-iron oxide. Examples of rectangular magnetic powder include cobalt ferrite, which has a cubic shape. These magnetic particles are oriented during the manufacturing process of the magnetic recording medium 10.

[0069] According to one preferred embodiment of the present technology, the magnetic powder may preferably comprise a powder of nanoparticles containing ε-iron oxide (hereinafter referred to as "ε-iron oxide particles"). ε-iron oxide particles can achieve high coercivity even in their fine size. It is preferable that the ε-iron oxide contained in the ε-iron oxide particles has a preferential crystal orientation in the thickness direction (perpendicular direction) of the magnetic recording medium 10.

[0070] The ε-iron oxide particles are spherical or nearly spherical, or cubic or nearly cubic. Because of the shape of the ε-iron oxide particles, when used as magnetic particles, the contact area between particles in the thickness direction of the medium can be reduced, and particle aggregation can be suppressed, compared to when hexagonal plate-shaped barium ferrite particles are used as magnetic particles. This improves the dispersibility of the magnetic powder, resulting in a better SNR (Signal-to-Noise Ratio).

[0071] The epsilon iron oxide particles have a core-shell structure or a Janus structure. Specifically, the epsilon iron oxide particles have a core and a two-layered shell structure surrounding the core. The two-layered shell structure includes a first shell portion provided on the core and a second shell portion provided on the first shell portion. In the present technology, the core-shell structure may be used to control the surface activity of the magnetic powder, thereby suppressing the capture of fatty acids.

[0072] The core portion contains ε-iron oxide. The ε-iron oxide contained in the core portion preferably has ε-Fe2O3 crystals as a main phase, and more preferably is composed of a single phase ε-Fe2O3.

[0073] The first shell portion covers at least a portion of the periphery of the core portion. Specifically, the first shell portion may cover a portion of the periphery of the core portion, or may cover the entire periphery of the core portion. From the viewpoint of ensuring sufficient exchange coupling between the core portion and the first shell portion and improving magnetic properties, it is preferable that the first shell portion covers the entire surface of the core portion.

[0074] The first shell portion is a so-called soft magnetic layer and may contain a soft magnetic material such as α-Fe, a Ni-Fe alloy, or an Fe-Si-Al alloy. The α-Fe may be obtained by reducing ε-iron oxide contained in the core portion.

[0075] The second shell portion is an oxide coating serving as an anti-oxidation layer. The second shell portion may contain α-iron oxide, aluminum oxide, or silicon oxide. The α-iron oxide may contain, for example, at least one iron oxide selected from Fe3O4, Fe2O3, and FeO. When the first shell portion contains α-Fe (soft magnetic material), the α-iron oxide may be obtained by oxidizing the α-Fe contained in the first shell portion.

[0076] The presence of the first shell portion in the ε-iron oxide particles as described above ensures thermal stability, thereby maintaining a high coercivity Hc of the core portion alone and / or adjusting the coercivity Hc of the entire ε-iron oxide particle (core-shell particle) to a coercivity Hc suitable for recording. Furthermore, the presence of the second shell portion in the ε-iron oxide particles as described above prevents deterioration of the properties of the ε-iron oxide particles due to rust or other damage caused by exposure to air during or before the manufacturing process of the magnetic recording medium 10. Therefore, deterioration of the properties of the magnetic recording medium 10 can be suppressed.

[0077] The ε-iron oxide particles may have a shell part with a single-layer structure. In this case, the shell part has the same structure as the first shell part. However, from the viewpoint of suppressing deterioration of the properties of the ε-iron oxide particles, it is more preferable that the ε-iron oxide particles have a shell part with a two-layer structure.

[0078] The ε-iron oxide particles may contain an additive instead of a core-shell structure, or may have a core-shell structure and contain an additive. In these cases, part of the Fe in the ε-iron oxide particles is substituted with the additive. By containing an additive in the ε-iron oxide particles, the coercivity Hc of the entire ε-iron oxide particles can be adjusted to a coercivity Hc suitable for recording, thereby improving ease of recording. The additive is a metal element other than iron, preferably a trivalent metal element, more preferably one or more selected from the group consisting of aluminum (Al), gallium (Ga), and indium (In). Specifically, the ε-iron oxide containing additives is ε-Fe 2-x M xO3 crystal (wherein M is a metal element other than iron, preferably a trivalent metal element, more preferably one or more selected from the group consisting of Al, Ga, and In. x is, for example, 0 <x<1である。)である。

[0079] According to another preferred embodiment of the present technology, the magnetic powder may be barium ferrite (BaFe) magnetic powder. The barium ferrite magnetic powder includes magnetic particles of iron oxide with barium ferrite as the main phase (hereinafter referred to as "barium ferrite particles"). The barium ferrite magnetic powder has high reliability in data recording, for example, because the coercive force does not decrease even in a high-temperature, high-humidity environment. From this perspective, the barium ferrite magnetic powder is preferable as the magnetic powder.

[0080] The average particle size of the barium ferrite magnetic powder may be 50 nm or less, more preferably 10 nm or more and 40 nm or less, and even more preferably 12 nm or more and 25 nm or less.

[0081] When the magnetic layer 13 contains barium ferrite magnetic powder as the magnetic powder, the average thickness t m [nm] is preferably 0.08 μm or less, more preferably 0.07 μm or less, and even more preferably 0.06 μm or less. The coercive force Hc measured in the thickness direction (perpendicular direction) of the magnetic recording medium 10 is preferably 160 kA / m or more and 280 kA / m or less, more preferably 165 kA / m or more and 275 kA / m or less, and even more preferably 170 kA / m or more and 270 kA / m or less.

[0082] According to yet another preferred embodiment of the present technology, the magnetic powder may be cobalt ferrite magnetic powder. The cobalt ferrite magnetic powder includes magnetic particles of iron oxide having cobalt ferrite as a main phase (hereinafter referred to as "cobalt ferrite magnetic particles"). The cobalt ferrite magnetic particles preferably have uniaxial anisotropy. The cobalt ferrite magnetic particles have, for example, a cubic or nearly cubic shape. The cobalt ferrite is cobalt ferrite containing Co. The cobalt ferrite may further include one or more elements selected from the group consisting of Ni, Mn, Al, Cu, and Zn in addition to Co.

[0083] Cobalt ferrite has, for example, an average composition represented by the following formula (1). Co x M y FeO z ···(1) (In formula (1), M is, for example, one or more metals selected from the group consisting of Ni, Mn, Al, Cu, and Zn. x is a value within the range of 0.4≦x≦1.0. y is a value within the range of 0≦y≦0.3, with the proviso that x and y satisfy the relationship (x+y)≦1.0. z is a value within the range of 3≦z≦4. A portion of Fe may be substituted with another metal element.)

[0084] The average particle size of the cobalt ferrite magnetic powder is preferably 25 nm or less, more preferably 23 nm or less. The coercive force Hc of the cobalt ferrite magnetic powder is preferably 2500 Oe or more, more preferably 2600 Oe or more and 3500 Oe or less.

[0085] According to yet another preferred embodiment of the present technology, the magnetic powder may include a powder of nanoparticles containing hexagonal ferrite (hereinafter referred to as "hexagonal ferrite particles"). The hexagonal ferrite particles have, for example, a hexagonal plate shape or an approximately hexagonal plate shape. The hexagonal ferrite may preferably contain at least one of Ba, Sr, Pb, and Ca, more preferably at least one of Ba and Sr. Specifically, the hexagonal ferrite may be, for example, barium ferrite or strontium ferrite. Barium ferrite may further contain at least one of Sr, Pb, and Ca in addition to Ba. Strontium ferrite may further contain at least one of Ba, Pb, and Ca in addition to Sr. More specifically, hexagonal ferrites have the general formula MFe 12 O 19 Here, M is, for example, at least one metal selected from Ba, Sr, Pb, and Ca, preferably at least one metal selected from Ba and Sr. M may be a combination of Ba and one or more metals selected from the group consisting of Sr, Pb, and Ca. M may also be a combination of Sr and one or more metals selected from the group consisting of Ba, Pb, and Ca. In the above general formula, part of Fe may be substituted with another metal element. When the magnetic powder includes a powder of hexagonal ferrite particles, the average particle size of the magnetic powder may be preferably 50 nm or less, more preferably 10 nm or more and 40 nm or less, and even more preferably 15 nm or more and 30 nm or less.

[0086] (first particle)

[0087] The first particles are electrically conductive. The first particles may be fine particles primarily composed of carbon, preferably carbon particles, and examples of such carbon particles include carbon black. Examples of carbon black that may be used include Asahi #15 and #15HS from Asahi Carbon Co., Ltd. Hybrid carbon, in which carbon is attached to the surface of silica particles, may also be used.

[0088] (second particle)

[0089] The second particles may have a Mohs hardness of 7 or more, preferably 7.5 or more, more preferably 8 or more, and even more preferably 8.5 or more, from the viewpoint of suppressing deformation due to contact with a magnetic head. The Mohs hardness of the second particles may be preferably 9.5 or less, from the viewpoint of suppressing head wear. The second particles may be preferably inorganic particles, such as α-Al2O3 (α-alumina) with an alpha conversion rate of 90% or more, β-Al2O3 (β-alumina), γ-Al2O3 (γ-alumina), silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, acicular α-iron oxide obtained by dehydrating and annealing magnetic iron oxide raw materials, optionally surface-treated with aluminum and / or silica, and diamond powder. The secondary particles are preferably alumina particles such as α-Al2O3 (α-alumina), β-Al2O3 (β-alumina), γ-Al2O3 (γ-alumina), or silicon carbide. These secondary particles may be acicular, spherical, cubic, or other shapes, but particles with angular shapes are preferred because they have high abrasiveness.

[0090] (Average height of protrusions formed by secondary particles)

[0091] The second particles form protrusions on the surface on the magnetic layer side.

[0092] The average height (H2) of the protrusions formed by the second particles may be 7 nm or less, preferably 6.5 nm or less, more preferably 6.0 nm or less, even more preferably 5.5 nm or less, and even more preferably 5.3 nm or less. When the magnetic recording medium has an average height (H2) of the protrusions formed by the second particles within the above numerical range, the spacing between the magnetic head and the magnetic recording medium is reduced, the occurrence of an increase in friction due to multiple runs is reduced, and the abrasive force against the magnetic head can be maintained appropriately.

[0093] Furthermore, the lower limit of the average height (H2) of the protrusions formed by the secondary particles is not particularly limited, but may be, for example, preferably 2.0 nm or more, more preferably 2.5 nm or more, and even more preferably 3.0 nm or more.

[0094] (lubricant)

[0095] The magnetic layer 13 contains a lubricant. The lubricant may be one or more selected from fatty acids and fatty acid esters, and preferably contains both fatty acids and fatty acid esters. The fatty acid may preferably be a compound represented by the following general formula (1) or (2). For example, the fatty acid may contain one or both of a compound represented by the following general formula (1) and a compound represented by the following general formula (2). The fatty acid ester may preferably be a compound represented by the following general formula (3) or (4). For example, the fatty acid ester may contain either or both of a compound represented by the following general formula (3) and a compound represented by the following general formula (4). When the lubricant contains either or both of a compound represented by general formula (1) and a compound represented by general formula (2), and / or either or both of a compound represented by general formula (3) and a compound represented by general formula (4), damage to the magnetic head can be prevented and a decrease in output can be suppressed. CH3(CH2) kCOOH (1) (However, in general formula (1), k is an integer selected from the range of 14 or more and 22 or less, more preferably from the range of 14 or more and 18 or less.) CH3(CH2) n CH=CH(CH2) m COOH (2) (However, in the general formula (2), the sum of n and m is an integer selected from the range of 12 to 20, more preferably from the range of 14 to 18.) CH3(CH2) p COO(CH2) q CH3···(3) (In general formula (3), p is an integer selected from the range of 14 or more and 22 or less, more preferably 14 or more and 18 or less, and q is an integer selected from the range of 2 or more and 5 or less, more preferably 2 or more and 4 or less.) CH3(CH2) r COO-(CH2) s CH(CH3)2 (4) (In the general formula (4), r is an integer selected from the range of 14 to 22, and s is an integer selected from the range of 1 to 3.)

[0096] Specific examples of fatty acids and fatty acid esters include the following: Fatty acids include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, and linolenic acid.

[0097] Examples of fatty acid esters include butyl caprate, octyl caprylate, ethyl laurate, butyl laurate, octyl laurate, ethyl myristate, butyl myristate, octyl myristate, 2-ethylhexyl myristate, ethyl palmitate, butyl palmitate, octyl palmitate, 2-ethylhexyl palmitate, ethyl stearate, butyl stearate, isobutyl stearate, octyl stearate, 2-ethylhexyl stearate, amyl stearate, isoamyl stearate, 2-ethylpentyl stearate, 2-hexyldecyl stearate, isotridecyl stearate, stearic acid amide, stearic acid alkyl amide, and butoxyethyl stearate.

[0098] (binder)

[0099] The binder is preferably a resin having a structure in which a crosslinking reaction has been imparted to a polyurethane resin or a vinyl chloride resin. However, the binder is not limited to these, and other resins may be appropriately blended depending on the physical properties required for the magnetic recording medium 10. The resin to be blended is not particularly limited as long as it is a resin that is generally used in coating-type magnetic recording media 10.

[0100] Examples of the binder include polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-vinyl chloride-vinylidene chloride copolymer, acrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinyl chloride copolymer, methacrylic acid ester-ethylene copolymer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose), styrene-butadiene copolymer, polyester resin, amino resin, and synthetic rubber.

[0101] Furthermore, a thermosetting resin or a reactive resin may be used as the binder, and examples of such a resin include a phenolic resin, an epoxy resin, a urea resin, a melamine resin, an alkyd resin, a silicone resin, a polyamine resin, and a urea-formaldehyde resin.

[0102] Furthermore, to improve the dispersibility of the magnetic powder, polar functional groups such as -SO3M, -OSO3M, -COOM, and P=O(OM)2 may be introduced into each of the binders described above, where M is a hydrogen atom or an alkali metal such as lithium, potassium, or sodium.

[0103] Furthermore, the polar functional groups include -NR1R2 and -NR1R2R3 + X - Side chain type with terminal group of >NR1R2 + X - In the formula, R1, R2, and R3 are hydrogen atoms or hydrocarbon groups, and X -is a halogen ion such as fluorine, chlorine, bromine, or iodine, or an inorganic or organic ion. Polar functional groups include —OH, —SH, —CN, and epoxy groups.

[0104] (additives)

[0105] The magnetic layer 13 may further contain non-magnetic reinforcing particles such as aluminum oxide (α, β, or γ alumina), chromium oxide, silicon oxide, diamond, garnet, emery, boron nitride, titanium carbide, silicon carbide, titanium carbide, titanium oxide (rutile or anatase titanium oxide), etc.

[0106] (Coating agent)

[0107] The magnetic layer 13 may contain a coating agent to coat the surface of the magnetic powder. Examples of such coating agents include organic acids having one or more polar groups such as carboxylic acid, phosphonic acid, and sulfonic acid, as well as their metal salts that function as acid groups, coupling agents (silane, aluminum, titanium, etc.), carbon, metal oxides, and hydroxides (aluminum, yttrium, etc.). Examples of organic acids include acetic acid, oxalic acid, citric acid, malonic acid, succinic acid, glutaric acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, benzoic acid, toluic acid, p-hydroxybenzoic acid, naphthoic acid, naphthalenedicarboxylic acid, hydroquinone, phenylphosphonic acid, benzylphosphonic acid, phenethylphosphonic acid, diphenylmethylphosphonic acid, biphenylphosphonic acid, benzylphenylphosphonic acid, toluylphosphonic acid, hexylphosphonic acid, octylphosphonic acid, nonylphosphonic acid, decylphosphonic acid, and the like. sulfonic acid, undecylphosphonic acid, dodecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, benzenesulfonic acid, p-toluenesulfonic acid, hexylbenzenesulfonic acid, octylbenzenesulfonic acid, decylbenzenesulfonic acid, undecylbenzenesulfonic acid, dodecylbenzenesulfonic acid, tridecylbenzenesulfonic acid, tetradecylbenzenesulfonic acid, hexadecylbenzenesulfonic acid, octadecylbenzenesulfonic acid, and naphthalenesulfonic acid.

[0108] (Nonmagnetic layer (base layer))

[0109] The non-magnetic layer (underlayer) 12 is a non-magnetic layer containing non-magnetic powder and a binder as its main components. The above description of the binder contained in the magnetic layer 13 also applies to the binder contained in the non-magnetic layer 12. The non-magnetic layer 12 may further contain at least one additive selected from the group consisting of first particles, a lubricant, a curing agent, and a rust inhibitor, as necessary.

[0110] The average thickness of the nonmagnetic layer 12 is preferably 1.2 μm or less, more preferably 1.0 μm or less, 0.9 μm or less, 0.8 μm or less, or 0.7 μm or less, and even more preferably 0.6 μm or less. There is no particular lower limit to the average thickness of the nonmagnetic layer 12, but it is preferably 0.2 μm or more, and more preferably 0.3 μm or more.

[0111] (Non-magnetic powder)

[0112] The non-magnetic powder contained in the non-magnetic layer 12 may include, for example, at least one type selected from inorganic particles and organic particles. One type of non-magnetic powder may be used alone, or two or more types of non-magnetic powder may be used in combination. The inorganic particles may include, for example, one or a combination of two or more types selected from metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. More specifically, the inorganic particles may be, for example, one or two or more types selected from iron oxyhydroxide, hematite, titanium oxide, and carbon black. The shape of the non-magnetic powder may be, for example, acicular, spherical, cubic, plate-like, or other shapes, but is not particularly limited to these.

[0113] (Coating agent)

[0114] Non-magnetic layer 12 may contain a coating agent to coat the surface of the non-magnetic powder. Such a coating agent may be the same as that contained in magnetic layer 13. Therefore, a description of the coating agent will be omitted.

[0115] (Back layer)

[0116] The back layer 14 can contain a binder and non-magnetic powder. The back layer 14 may also contain various additives such as a lubricant, a curing agent, an antistatic agent, and an organic acid, as necessary. The above explanations regarding the binder and non-magnetic powder contained in the non-magnetic layer 12 also apply to the binder and non-magnetic powder contained in the back layer 14.

[0117] The average particle size of the inorganic particles contained in the back layer 14 is preferably 10 nm or more and 150 nm or less, and more preferably 15 nm or more and 110 nm or less. The average particle size of the inorganic particles is determined in the same manner as the average particle size D of the magnetic powder described above.

[0118] The average thickness t of the back layer 14 b The average thickness t of the back layer 14 is preferably 0.6 μm or less, more preferably 0.5 μm or less, and even more preferably 0.4 μm or less, 0.3 μm or less, 0.25 μm or less, or 0.2 μm or less. b When the average thickness (average total thickness) t of the magnetic recording medium 10 is within the above range, T A T Even when the thickness is set to ≦5.7 μm, the average thickness of the nonmagnetic layer 12 and the base layer 11 can be kept large, thereby maintaining the running stability of the magnetic recording medium 10 within a recording / reproducing device.

[0119] (3) Physical properties and structure

[0120] (Extraction rate of fatty acids and / or fatty acid esters)

[0121] <Advance preparation> A. Setting the sample mount Cut out four pieces of graph paper and draw 1m marker lines six squares inward on both ends so that the center is 1m in size. Figure 18 shows an example of a sample mount used to measure the extraction rate. As shown in Figure 18, mark an inverted triangle 50cm in the center of the graph paper. Place the graph paper parallel to the desk and secure both ends of the graph paper with double-sided tape. Attach double-sided tape so that it covers the two 1m marker lines and set the sample mount in place.

[0122] B. Preparation of a mixed solvent of acetonitrile and ultrapure water (acetonitrile:ultrapure water = 100:3) Pour 30 ml of ultrapure water into 1000 ml of acetonitrile. After closing the lid, shake gently up and down, and with the lid loosened, degas the container in an ultrasonic cleaner for 15 minutes.

[0123] C. Preparation of aluminum lid Place the black lid, white rubber, and aluminum sheet.

[0124] D. Syringe Preparation Place the filter on the outer shaft of the syringe. Leave the inner shaft out as well.

[0125] E. Preparation of Standard Reagents The type of standard reagent varies depending on the fatty acid or fatty acid ester used. The concentration is also optional. As an example, let's use stearic acid as the fatty acid and butyl stearate as the fatty acid ester. The stearic acid standard reagent is prepared as follows: Weigh out 4.0 mg, 10.0 mg, and 30.0 mg of stearic acid, weigh out a solvent of acetonitrile / water = 100 / 3, and measure up to 200 mL each. The butyl stearate standard reagent is prepared as follows: Weigh out 10.0 mg, 30.0 mg, and 40.0 mg of butyl stearate, weigh out a solvent of acetonitrile / water = 100 / 3, and measure up to 200 mL each. Prepare a standard reagent of stearic acid (manufactured by Junsei Chemical Co., Ltd., purity 95.0%). Prepare a standard reagent of butyl stearate (manufactured by Junsei Chemical Co., Ltd., purity 95.0%).

[0126] <Reversed-phase liquid chromatography setup> An Ultimate 3000 (Thermo) column (ODS-2 5 μm, 4.6 × 150 mm, GL Sciences) was used for reversed-phase liquid chromatography (HPLC). The pump, autosampler, differential refractometer (Shodex RI-101, Showa Denko, set temperature: 30°C), and PC were all powered on. The pump was purged for 5 minutes. The autosampler was washed. The software was started. The liquid began to flow when the flow rate / pressure was increased to 2 ml, and the system was allowed to stand for at least 1 hour until the liquid stabilized. The measurement conditions were set as follows: mobile phase acetonitrile / water = 100 / 3 (volume ratio), solvent acetonitrile / water = 100 / 3, column temperature 40°C, measurement time 10 minutes, flow rate 2 ml per minute, and injection volume 200 μl.

[0127] <Preparation of standard reagents> Place the prepared standard reagent in an ultrasonic cleaner for 15 minutes. Once the ultrasonic treatment is complete, insert the syringe with the filter set into the vial and pour the standard reagent directly into the syringe. Fill the vial with the standard reagent. Press the center stem to push the liquid into the vial. Once it is filled up to the shoulder of the vial, close the aluminum lid. Return the standard reagent remaining in the syringe to the screw cap vial through the filter.

[0128] <Sample collection> Unwind the magnetic tape T housed in cartridge 10A and cut it into approximately 5m lengths 20m longitudinally from the joint between the magnetic tape T and leader tape LT. Using the lines on the graph paper, attach the magnetic tape to the double-sided tape on the sample mount, overlapping the Mag / Back alternately in parallel. Be careful not to apply too much tension when attaching the magnetic tape. Discard the P / C surface and collect five 1m strips of magnetic tape. Place a ruler along the 1m marker line on the sample mount and cut out 1m of magnetic tape with a cutter. Gather the five strips of magnetic tape together, pick up the center indicated by the inverted triangle mark with tweezers, fold it in half, and grasp the curled edge to create a wrinkle. Separate the magnetic tapes one by one and place them into a 120ml round-bottom flask, then cover with aluminum foil.

[0129] A. 5-minute extraction Measure 60 ml of hexane into a 100 ml graduated cylinder. Set the stopwatch for 5 minutes. Place the 120 ml screw tube containing the sample in an automatic shaker placed in a 25°C environment and leave the aluminum lid open. Place the measured 60 ml of hexane into a 120 ml round-bottom flask, put the aluminum lid on, and turn on the stopwatch and automatic shaker simultaneously to begin shaking (set the automatic shaker speed to 300 rpm). Five minutes after shaking begins, measure 50 ml of sample into a 100 ml graduated cylinder. Transfer the sample from the graduated cylinder to an eggplant flask. Insert the eggplant flask containing the sample into the eggplant flask mounting port of the evaporator and secure it in place. Start the evaporator, set the eggplant flask speed to 50 rpm, and rotate the eggplant flask. Begin drawing a vacuum to 160 hPa. Submerge the eggplant flask in a water bath. The hexane will evaporate in about 4 minutes, leaving only the fatty acid or fatty acid ester in the eggplant flask. Once the hexane has completely evaporated, remove the recovery flask from the water bath. Release the vacuum and release the pressure to atmospheric pressure (around 1013 hPa). Stop the evaporator from rotating. Remove the recovery flask and let it dry. B. Solvent substitution After the hexane has been removed by the evaporator, 5 ml of a mixed solvent of acetonitrile and ultrapure water is pipetted into the dried recovery flask and poured into the neck. Place the aluminum lid on and shake while holding the neck of the recovery flask. Apply ultrasound for 15 minutes. After ultrasonic treatment, shake the recovery flask again and add all of the liquid to the vial with a syringe equipped with a 0.5 μm filter attached. Push in the center stem, fill the vial with liquid up to the shoulder, then close the lid and discard any liquid remaining in the syringe. C.HPLC measurement After the reverse phase liquid chromatography (HPLC) has been started up, the measurement is started.

[0130] <Total amount extraction> The preparatory steps, standard sample preparation, and sample collection are the same as those for the 5-minute extraction, so the explanation will be omitted.

[0131] Measure 60 ml of hexane into a 100 ml graduated cylinder. Set the stopwatch to 1 hour. Place the 110 ml screw cap containing the sample in an ultrasonicator (UT-105HS, SHARP) with the aluminum lid open. The ultrasonicator has a water bath (water temperature: 40-50 °C). Fill the water bath with water up to the upper water level line and set the ultrasonic output to 100%. Place 60 ml of the measured hexane into the 120 ml screw cap, replace the aluminum lid, and simultaneously turn on the stopwatch and ultrasonicator to begin extraction. One hour after turning on the ultrasonicator, use an evaporator to remove the hexane from the sample in the 110 ml screw cap using the same method as for the 5-minute extraction. Then, perform solvent replacement using the same procedure as for the 5-minute extraction, except add 5 ml of a mixed solvent of acetonitrile and ultrapure water (if the concentration is too high and the HPLC peak area is off, use 10 ml). Then, perform measurement.

[0132] <Data analysis>

[0133] Data analysis is carried out using the following procedure. (1) Determine the area value of the standard reagent and create a calibration curve (in the form y=ax). (2) Determine the area value of the measurement sample and calculate the concentration from the calibration curve (the method of drawing the peak area should be consistent with that of the standard reagent). Then, determine the amount of fatty acid (mg) or fatty acid ester (mg) in 5 ml (or 10 ml) of acetonite solution. (3) The amount of fatty acid or fatty acid ester was calculated based on the following formula: 2 ) Extraction amount = (amount of fatty acid or fatty acid ester * (60 / 50)) / tape area Amount of fatty acid or fatty acid ester = the value obtained in (2) above Tape area 5m = 0.06325m 2 (1 / 2 inch x length [m]) *The amount of fatty acids or fatty acid esters was measured in 50 ml of the 60 ml extracted with hexane, so corrections were made.

[0134] (Protrusion height)

[0135] As described below, the height of the protrusions formed by the second particles is measured by performing shape analysis using an atomic force microscope (hereinafter referred to as an AFM) on the same location of the measurement sample, and by distinguishing components obtained by image analysis using the brightness difference due to the difference in the amount of secondary electron emission of the first particles and the second particles from FE-SEM images taken by the FE-SEM. The height of the protrusions can be measured using the AFM, and it is possible to identify whether each protrusion is formed by the first particles or the second particles using the FE-SEM. The image obtained by the AFM on the same location and the image obtained by the FE-SEM on the certain region are overlaid to obtain a composite image, and the type of particle forming each protrusion (whether it is the first particle or the second particle) can be associated with the height of each protrusion from the obtained composite image. Below, we will explain how to measure the height of protrusions using AFM, how to identify the type of particles that form the protrusions using FE-SEM, and how to associate the height of the protrusions with the type of particles that form the protrusions.

[0136] (Method for measuring protrusion height using an atomic force microscope (AFM)) In this technique, the height of the protrusions formed by the second particles is determined as follows. First, a measurement sample is prepared by cutting a portion of the magnetic recording medium 10 from the user data area (24 m or more from the leader pin) in an LTO cartridge to a size that fits on a sample stage for SEM observation. Next, markings are made on the surface of the measurement sample, avoiding the center of the measurement sample. Marking methods include forming linear or dot-shaped depressions on the magnetic recording medium 10 using a manipulator or a nine-denter, or forming protrusions on the magnetic recording medium 10 using silver paste or the like. Note that, since the AFM scans the marked area with a probe, depending on the condition of the marked area, the probe tip may become contaminated, making it difficult to obtain an accurate shape image. Therefore, it is preferable to make the markings small and shallow to prevent contamination of the probe. Next, the shape of the marked area on the measurement sample surface is analyzed using an AFM. Because the marked area is concave, measurements are made with the AFM at a field of view of 5 μm × 5 μm, with the marked area positioned as close to the edge of the field of view as possible. Note that protrusions around the marked area are not measured. Next, measurements are performed over a 10 μm × 10 μm field of view, a marking area is determined, and an unmarked area is measured over a 5 μm × 5 μm field of view in accordance with the marking area. The measurement conditions for the shape analysis are as follows: For the second particles, if 20 or more particles can be identified in one AFM field of view from one measurement sample, one field of view is measured using the AFM. For the second particles, if fewer than 20 particles can be identified in one AFM field of view, multiple fields (e.g., 3 to 5) are measured from one measurement sample. For the second particles, 20 points identified as particles are obtained through binarization processing, and the 20 AFM measurement values ​​are averaged, with the resulting average value being the protrusion height. The shape analysis can provide information on the surface shape, protrusion analysis, and protrusion height distribution. Figure 7 shows an example of an image depicting an example of a surface shape captured by the AFM. Figure 8 shows an example of a protrusion analysis result obtained by the AFM. Figure 9 shows an example of a protrusion height distribution. From the obtained information, data such as the number of protrusions formed and the height of the protrusions formed by the particles can be obtained.

[0137] <AFM Measurement Conditions> Equipment: AFM Dimension 3100 microscope (with NanoscopeIV controller) (Digital Instruments, USA) Measurement mode: Tapping Tapping frequency during tuning: 200 - 400 kHz Cantilever: SNL-10 (manufactured by Bruker) Scan size: 5μm × 5μm Scan rate: 1Hz Scan line: 256

[0138] <Method for calculating the reference plane when calculating the protrusion height> The AFM image is divided into 256 × 256 (= 65,536) measurement points, and the height Z(i) (i: measurement point number, i = 1 - 65,536) is measured at each measurement point. The measured heights Z(i) of each measurement point are simply averaged (arithmetic mean) to obtain the average height (reference plane) Z ave (=(Z(1) + Z(2) + ··· + Z(65,536)) / 65,536 ) is obtained.

[0139] (Method for identifying the type of particles forming protrusions using FE-SEM) The marked part of the measurement sample is imaged using a field emission scanning electron microscope (FE-SEM) under the FE-SEM measurement conditions described below to obtain a FE-SEM image. Figure A in Figure 10 is an example of a FE-SEM image. From the obtained FE-SEM image, the type of particles forming protrusions can be identified by utilizing the luminance difference due to the difference in the secondary electron emission amounts of the first particles and the second particles. The image processing for this identification will be described later. Also, the positions of the protrusions formed by the first particles and the second particles in the FE-SEM image are identified.

[0140] <FE-SEM Measurement Conditions> Equipment: HITACHI S-4800 (manufactured by Hitachi High-Technologies Corporation) Field of view angle: 5.1μm × 3.8μm Acceleration voltage: 5kV Measurement magnification: 25000x

[0141] The obtained FE-SEM image (Figure A in Figure 10) is binarized using the image processing software Image J under the two processing conditions described below. From the image obtained by binarization, information can be obtained about the number of protrusions formed by each of the primary particles and secondary particles, the average area per protrusion, the total area of ​​the protrusions, and the diameter of the protrusions (Feret diameter). Note that during binarization, the conditions are changed as follows for the highly luminous secondary particles (white areas in Figure A in Figure 10) and the less luminous primary particles (black areas in Figure A in Figure 10).

[0142] <Binarization processing conditions for obtaining information about the first particle>

[0143] Software: Image J Ver 1.44p Binarization threshold: Threshold(0.65) Binarization target size: 0.002μm-infinity

[0144] <Binarization processing conditions for obtaining information about secondary particles>

[0145] Software: Image J Ver 1.44p Binarization threshold: Threshold(220,255) Binarization target size: 0.001μm-infinity

[0146] Figure 10B is an image showing the position distribution of protrusions formed by the secondary particles (alumina particles) obtained by binarizing the FE-SEM image of Figure 10A under the binarization conditions for the secondary particles (alumina particles). The following information about the secondary particles was obtained from the resulting image.

[0147] <Information about the obtained second particle>

[0148] Quantity: 58 Average area: 0.003μm 2 Total area: 0.198 μm 2 Feret diameter: 0.091 μm

[0149] Figure 10C shows the positional distribution of protrusions formed by the first particles (carbon black particles) after binarizing the FE-SEM image of Figure 10A under the binarization conditions for the first particles (carbon black particles). The following information about the first particles was obtained from the resulting image.

[0150] <Information about the first particle obtained>

[0151] Quantity: 55 Average area: 0.005μm 2 Total area: 0.262 μm 2 Feret diameter: 0.013 μm

[0152] (Method of Corresponding Protrusion Height to the Type of Particles That Form the Protrusions) The obtained AFM image is overlaid with the FE-SEM image before binarization to obtain a composite image. Using the composite image, the particles forming each protrusion are identified as either primary particles or secondary particles. For example, Figure C in Figure 11 is a composite image obtained by superimposing an AFM image (Figure B) and an FE-SEM image (Figure A) so that the positions of the corresponding protrusions coincide. In Figure 11, different marks are attached to the positions of the protrusions formed by the first particles P1 and the second particles P2, which are present in the FE-SEM image (Figure A) before image synthesis, and which are determined by the binarization process, so that the positions can be distinguished. Similarly, different marks are attached to the positions of the protrusions formed by the first particles (carbon black particles) P1 and the second particles (alumina particles) P2, which are present in the AFM image (Figure B) before image synthesis, so that the positions can be distinguished. From the composite image obtained by superimposing an AFM image (Figure B) and an FE-SEM image (Figure A) so that the positions of the corresponding protrusions coincide, it is possible to determine whether each protrusion was formed by the first particles P1 or the second particles P2. In Figure 11 (Figure B), the marked area was measured with an AFM at a viewing angle of 10 μm × 10 μm, and then the area without the marking was measured at a viewing angle of 5 μm × 5 μm, so the marking does not exist in the image.

[0153] Next, the height of each protrusion in the composite image is measured using AFM analysis software (Software version 5.12 Rev.B for Dimension 3100, manufactured by Veeco). As described above, the type of particle forming each protrusion (whether it is a first particle or a second particle) is identified, and therefore the identified particle type is associated with the measured height. For example, Fig. 12 is an enlarged view of a composite image obtained by superimposing an AFM image and an FE-SEM image. Fig. 13 is a diagram showing the results of AFM analysis (measurement results of protrusion height) for Line 1 (Line 1) set at an arbitrary position in Fig. 12. As shown in Fig. 13, the height of the protrusions formed by the second particles (alumina particles) present on Line 1 can be identified. In this way, the height of the protrusions can be identified from the composite image and the AFM analysis results.

[0154] (average height of protrusions)

[0155] The average height of the protrusions formed by the secondary particles is determined from the information on the height of the protrusions obtained as described above. The average height of the protrusions can be determined, for example, from the cumulative frequency distribution of the protrusions formed by the secondary particles. For example, Fig. 14 is a diagram showing the cumulative frequency distribution of the height of the protrusions formed by the second particles (alumina particles). In Fig. 14, A indicates frequency, and B indicates cumulative %. Fig. 14 shows that the average height of the protrusions formed by the second particles (alumina particles) is 5.1 nm.

[0156] (adhesion) A so-called full volume test (full-length running test) is conducted, in which data is recorded and played back on the entire surface of the magnetic tape. The drive's magnetic head is then observed with an optical microscope to confirm whether the magnetic layer's constituent materials have adhered to the magnetic head. Next, the adhesion of the magnetic layer's constituent materials to the magnetic head after the full length running is evaluated using the following three-level criteria: [standard] ◯: No adhesion of the constituent material of the magnetic layer to the head was observed. △: Adhesion of the constituent material of the magnetic layer was observed only at the end portion of the tape running surface of the head where the tape edge runs. x: Adhesion of the constituent material of the magnetic layer was observed on any part of the tape running surface of the head. If the evaluation result is "good" or "fair," there will be no problems with the reliability of the magnetic tape. If the evaluation result is "x", head clogging occurs for a short period of time, and the total capacity of the cartridge becomes insufficient.

[0157] (output degradation) The output degradation due to magnetic head damage is evaluated according to the following procedure. (1) Measure the drive output (2T, 8T) and head resistance before evaluation. (2) Start the test in an ambient environment. Record the entire length of one cartridge. Once the test is complete, replace it with a new cartridge. (3) After every 25 turns, measure the drive output and head resistance to check for changes in output and head resistance. Check the degree of deterioration (dB) based on the drive output before evaluation. (4) Repeat the above procedure (3) up to 50 volumes. Next, the drive output degradation after 50 windings is evaluated using the following four-level criteria. [standard] ◎: Within 2.5dB ○: Within 3dB △:More than 3dB ×: 4dB or more If the evaluation result is "△", capacity loss, rewrite, and error rate will worsen. If it is "×", actual damage will occur.

[0158] (Average thickness (average total thickness) of magnetic recording medium (magnetic tape)) T )

[0159] Average thickness (average total thickness) of magnetic tape T T The upper limit of the average thickness t of the magnetic tape T is preferably 5.7 μm or less, 5.2 μm or less, more preferably 5.0 μm or less, even more preferably 4.6 μm or less, and particularly preferably 4.4 μm or less. T If the average thickness t of the magnetic tape T is 5.2 μm or less, the recording capacity that can be recorded in one data cartridge can be increased compared to that of a general magnetic tape. T The lower limit is not particularly limited, but is, for example, 3.5 μm or more.

[0160] Average thickness t of magnetic tape T Tis obtained as follows. First, the magnetic tape T housed in the cartridge 10A is unwound, and the magnetic tape T is cut into a length of 250 mm at a position 30 m in the longitudinal direction from the joint between the magnetic tape T and the leader tape LT to prepare a sample. Next, the thickness of the sample is measured at five positions using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, and these measurements are simply averaged (arithmetic mean) to obtain the average thickness t T The five measurement positions are selected at random from the sample so that they are different positions in the longitudinal direction of the magnetic tape T.

[0161] (Average thickness of non-magnetic layer (underlayer))

[0162] The average thickness of the nonmagnetic layer 12 is determined as follows. First, the magnetic tape T housed in the cartridge 10A is unwound, and three samples of 250 mm are cut from the magnetic tape T at three locations, 10 m, 30 m, and 50 m from the connection between the magnetic tape T and the leader tape LT, to prepare three samples. Next, each sample is thinned using a FIB method or other processing. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing the cross-sectional TEM images described below. The carbon layer is formed by vapor deposition on the surface of the magnetic tape T facing the magnetic layer 13 and the surface facing the back layer 14, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 13. The thinning is performed along the longitudinal direction of the magnetic tape T. That is, the thinning results in a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape T.

[0163] The cross section of each of the obtained thinned samples is observed under a transmission electron microscope (TEM) under the following conditions. Apparatus: TEM (Hitachi H9000NAR) Accelerating voltage: 300 kV Magnification: 100,000x Next, using the obtained TEM image, the thickness of the non-magnetic layer 12 is measured at at least 10 positions in the longitudinal direction of the magnetic tape T, and then the measured values ​​are simply averaged (arithmetic averaged) to obtain the average thickness (μm) of the non-magnetic layer 12.

[0164] (average thickness of base layer)

[0165] The average thickness of the base layer 11 is determined as follows. First, the magnetic tape T housed in the magnetic recording cartridge 10A is unwound, and a sample is prepared by cutting the magnetic tape T to a length of 250 mm at a position 30 m in the longitudinal direction from the joint between the magnetic tape T and the leader tape LT. In this specification, the "longitudinal direction" in the "longitudinal direction from the joint between the magnetic tape T and the leader tape LT" refers to the direction from one end on the leader tape LT side to the other end on the opposite side.

[0166] Next, all layers of the sample other than the base layer 11 (i.e., the non-magnetic layer (underlayer) 12, the magnetic layer 13, and the back layer 14) are removed using a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, using a Mitutoyo Laser Hologram (LGH-110C) as a measuring device, the thickness of the sample (base layer 11) is measured at five positions, and the measured values ​​are simply averaged (arithmetic mean) to calculate the average thickness of the base layer 11. Note that the five measurement positions are selected randomly from the sample so that they are each different from the others in the longitudinal direction of the magnetic tape T.

[0167] (Average thickness of back layer t b )

[0168] The upper limit of the average thickness of the back layer 14 is preferably 0.6 μm or less. If the upper limit of the average thickness of the back layer 14 is 0.6 μm or less, the thicknesses of the nonmagnetic layer (underlayer) 12 and the base layer 11 can be kept thick even when the average thickness of the magnetic tape T is 5.6 μm or less, thereby maintaining running stability of the magnetic tape T within a recording / reproducing device. The lower limit of the average thickness of the back layer 14 is not particularly limited, but is, for example, 0.2 μm or more.

[0169] The average thickness t of the back layer 14 b can be calculated as follows: First, the average thickness (average total thickness) of the magnetic tape T is T Measure the average thickness t T The method for measuring the average total thickness is as described below in "Average Thickness of Magnetic Tape." Next, the magnetic tape T housed in the cartridge 10A is unwound, and the magnetic tape T is cut into a length of 250 mm at a position 30 m longitudinally from the joint between the magnetic tape T and the leader tape LT to prepare a sample. Next, the back layer 14 of the sample is removed with a solvent such as MEK (methyl ethyl ketone) or dilute hydrochloric acid. Next, using a Mitutoyo Laser Hologram (LGH-110C), the thickness of the sample is measured at five positions, and these measurements are simply averaged (arithmetic average) to obtain the average thickness t B Then, the average thickness t of the back layer 14 is calculated using the following formula: b The five measurement positions are selected at random from the sample so that they are different positions in the longitudinal direction of the magnetic tape T. t b [μm]=t T [μm]-t B [μm]

[0170] (the average thickness of the magnetic layer t m )

[0171] The average thickness t of the magnetic layer 13 mis determined as follows. First, the magnetic tape T housed in the cartridge 10A is unwound, and three samples of 250 mm length are cut from the magnetic tape T at three locations, 10 m, 30 m, and 50 m from the connection between the magnetic tape T and the leader tape LT, in the longitudinal direction. Each sample is then thinned using a FIB method or similar. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing the cross-sectional TEM images described below. The carbon layer is formed by vapor deposition on the surface of the magnetic tape T facing the magnetic layer 13 and the surface facing the back layer 14, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 13. The thinning is performed along the longitudinal direction of the magnetic tape T. That is, the thinning results in a cross section parallel to both the longitudinal direction and the thickness direction of the magnetic tape T.

[0172] The cross section of each obtained sliced ​​sample is observed under a transmission electron microscope (TEM) under the following conditions to obtain a TEM image of each sliced ​​sample. Note that the magnification and acceleration voltage may be adjusted appropriately depending on the type of device. Apparatus: TEM (Hitachi H9000NAR) Accelerating voltage: 300 kV Magnification: 100,000x

[0173] Next, using the TEM image of each obtained sliced ​​sample, the thickness of the magnetic layer 13 is measured at 10 positions on each sliced ​​sample. The 10 measurement positions on each sliced ​​sample are randomly selected from the sample so that they are different positions in the longitudinal direction of the magnetic tape T. The measured values ​​of each obtained sliced ​​sample (thickness of the magnetic layer 13 at 30 points in total) are simply averaged (arithmetic average) to obtain an average value, which is the average thickness t of the magnetic layer 13. m Let [nm].

[0174] (average particle size of magnetic powder)

[0175] When the magnetic powder contains hexagonal ferrite particles, the average particle size and average aspect ratio of the magnetic powder can be determined as follows. First, the magnetic tape T housed in the cartridge 10A is unwound, and the magnetic tape T is cut out at a position 30 m longitudinally from the connection between the magnetic tape T and the leader tape LT. Next, the magnetic tape T to be measured is processed and thinned using a FIB method or the like. When using the FIB method, a carbon layer and a tungsten layer are formed as protective films as a pretreatment for observing the cross-sectional TEM image described below. The carbon layer is formed by vapor deposition on the surface of the magnetic tape T facing the magnetic layer 13 and the surface facing the back layer 14, and the tungsten layer is further formed by vapor deposition or sputtering on the surface facing the magnetic layer 13. The thinning is performed along the length (longitudinal direction) of the magnetic tape T. In other words, the thinning results in a cross section parallel to both the longitudinal and thickness directions of the magnetic tape T.

[0176] The cross section of the obtained thin sample is observed using a transmission electron microscope (H-9500 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 200 kV and a total magnification of 500,000 times, so as to include the entire magnetic layer 13 in the thickness direction of the magnetic layer 13, and a TEM photograph is taken. The number of TEM photographs prepared is such that 50 particles can be extracted that can measure the plate diameter DB and plate thickness DA (see Figure 15) shown below.

[0177] In this specification, the size of a hexagonal ferrite particle (hereinafter referred to as "particle size") is defined as the plate diameter DB, which is the longest diameter of the plate surface or base, when the particle shape observed in the TEM photograph is plate-like or columnar (however, the thickness or height is smaller than the longest diameter of the plate surface or base), as shown in FIG. 15. The thickness or height of the particle observed in the TEM photograph is defined as the plate thickness DA. When the plate surface or base of the particle observed in the TEM photograph is hexagonal, the longest diameter means the longest diagonal distance. When the thickness or height of a particle is not constant within a single particle, the thickness or height of the largest particle is defined as the plate thickness DA.

[0178] Next, 50 particles are selected from the TEM photograph based on the following criteria. Particles with parts outside the field of view of the TEM photograph are not measured, and only particles with a clear outline and that exist independently are measured. If particles overlap, those with a clear boundary between them and whose overall shape can be determined are measured as individual particles, but particles with unclear boundaries and whose overall shape cannot be determined are not measured as their shape cannot be determined.

[0179] Examples of TEM photographs are shown in Figures 16 and 17. In Figures 16 and 17, the particles indicated by arrows a and d are selected because their plate thickness (thickness or height) DA can be clearly confirmed. The plate thickness DA of each of the selected 50 particles is measured. The plate thicknesses DA thus obtained are simply averaged (arithmetic mean) to obtain the average plate thickness DA. ave Average plate thickness DA ave is the average particle plate thickness. Next, the plate diameter DB of each magnetic powder is measured. In order to measure the particle plate diameter DB, 50 particles whose particle plate diameter DB can be clearly confirmed are selected from the TEM photograph. For example, in Figures 16 and 17, the particles indicated by arrows b and c are selected because their plate diameter DB can be clearly confirmed. The plate diameter DB of each of the selected 50 particles is measured. The plate diameters DB thus determined are simply averaged (arithmetic averaged) to obtain the average plate diameter DB. ave Average plate diameter DB ave is the average grain size. And the average plate thickness DA ave and average plate diameter DB ave The average aspect ratio of the particles (DB ave / DA ave ) is found.

[0180] (average particle volume of magnetic powder)

[0181] The average particle volume of the magnetic powder can be calculated as follows: First, as described above in relation to the method for calculating the average particle size of the magnetic powder, the average plate thickness DA ave and average plate diameter DB aveNext, calculate the average particle volume V of the magnetic powder using the following formula:

[0182]

number

[0183] (Squareness ratio in the vertical direction Rs2)

[0184] The squareness ratio Rs2 in the perpendicular direction (thickness direction) of the magnetic recording medium of the present technology can be preferably 65% ​​or more, more preferably 67% or more, and even more preferably 70% or more. When the squareness ratio Rs2 is 65% or more, the perpendicular orientation of the magnetic powder is sufficiently high, resulting in a superior SNR. Therefore, superior electromagnetic conversion characteristics can be obtained. Furthermore, the servo signal shape is improved, making it easier to control on the drive side. In this specification, a magnetic recording medium being perpendicularly oriented may mean that the squareness ratio Rs2 of the magnetic recording medium is within the above numerical range (for example, 65% or more).

[0185] The squareness ratio Rs2 in the perpendicular direction is determined as follows. First, the magnetic tape T housed in the magnetic recording cartridge 10A is unwound, and the magnetic tape T is cut into a length of 250 mm at a position 30 m longitudinally from the joint between the magnetic tape T and the leader tape LT to prepare a sample. The sample is punched out to 6.25 mm x 64 mm and then folded in thirds to prepare a 6.25 mm x 8 mm measurement sample. Then, the MH hysteresis loop of the measurement sample (the entire magnetic tape T) corresponding to the perpendicular direction (thickness direction) of the magnetic tape T is measured using a VSM. Next, the coating films (underlayer 12, magnetic layer 13, back layer 14, etc.) are wiped off using acetone or ethanol, leaving only the base layer 11. The obtained base layer 11 is then punched out to 6.25 mm x 64 mm and then folded in thirds to prepare a 6.25 mm x 8 mm sample for background correction (hereinafter simply referred to as the "correction sample"). Thereafter, the MH hysteresis loop of the correction sample (base layer 11) corresponding to the perpendicular direction of the base layer 11 (the perpendicular direction of the magnetic recording medium 10) is measured using the VSM.

[0186] The MH hysteresis loop of the measurement sample (the entire magnetic tape T) and the MH hysteresis loop of the correction sample (base layer 11) are measured using a high-sensitivity vibration sample magnetometer "VSM-P7-15" manufactured by Toei Industry Co., Ltd. The measurement conditions are as follows: measurement mode: full loop, maximum magnetic field: 15 kOe, magnetic field step: 40 bits, time constant of locking amp: 0.3 sec, waiting time: 1 sec, number of MH averages: 20. After obtaining the MH hysteresis loop of the measurement sample (the entire magnetic tape T) and the MH hysteresis loop of the correction sample (base layer 11), background correction is performed by subtracting the MH hysteresis loop of the correction sample (base layer 11) from the MH hysteresis loop of the measurement sample (the entire magnetic tape T), and the MH hysteresis loop after background correction is obtained. This background correction calculation is performed using the measurement and analysis program included with the "VSM-P7-15 model."

[0187] The saturation magnetization Ms (emu) and residual magnetization Mr (emu) of the MH hysteresis loop after background correction are substituted into the following equation to calculate the squareness ratio Rs2 (%). Note that all of the above MH hysteresis loop measurements are performed at 25°C. Furthermore, no "demagnetizing field correction" is performed when measuring the MH hysteresis loop in the perpendicular direction to the magnetic tape T. Note that this calculation uses the measurement and analysis program included with the "VSM-P7-15 model." Squareness ratio Rs2(%)=(Mr / Ms)×100

[0188] (4) Manufacturing method of magnetic recording medium

[0189] Next, a method for manufacturing the magnetic recording medium 10 having the above-described configuration will be described. First, a paint for forming a non-magnetic layer (underlayer) is prepared by kneading and / or dispersing non-magnetic powder, a binder, etc. in a solvent. Next, a paint for forming a magnetic layer is prepared by kneading and / or dispersing magnetic powder, a binder, etc. in a solvent. The following solvents, dispersing devices, and kneading devices can be used, for example, to prepare the paint for forming a magnetic layer and the paint for forming a non-magnetic layer (underlayer).

[0190] Examples of solvents that can be used in preparing the coating material include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohol-based solvents such as methanol, ethanol, and propanol; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate, and ethylene glycol acetate; ether-based solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane; aromatic hydrocarbon-based solvents such as benzene, toluene, and xylene; and halogenated hydrocarbon-based solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and chlorobenzene. These solvents may be used singly or in combination.

[0191] Examples of kneading devices used in preparing the above-mentioned coating materials include, but are not limited to, continuous twin-screw kneaders, continuous twin-screw kneaders capable of multi-stage dilution, kneaders, pressure kneaders, and roll kneaders. Examples of dispersing devices used in preparing the above-mentioned coating materials include, but are not limited to, roll mills, ball mills, horizontal sand mills, vertical sand mills, spike mills, pin mills, tower mills, pearl mills (such as the "DCP Mill" manufactured by Eirich), homogenizers, and ultrasonic dispersers.

[0192] Next, a nonmagnetic layer (underlayer) forming paint is applied to one main surface of the base layer 11 and dried to form the nonmagnetic layer 12. Subsequently, a magnetic layer forming paint is applied to the nonmagnetic layer 12 and dried to form the magnetic layer 13 on the nonmagnetic layer 12. During drying, the magnetic powder is magnetically oriented in the thickness direction of the base layer 11, for example, using a solenoid coil. Alternatively, during drying, the magnetic powder may be magnetically oriented in the longitudinal direction (running direction) of the base layer 11 using a solenoid coil, and then magnetically oriented in the thickness direction of the base layer 11. Such magnetic field orientation treatment can reduce the ratio Hc2 / Hc1 of the coercivity in the perpendicular direction (Hc1) to the coercivity in the longitudinal direction (Hc2), thereby improving the degree of perpendicular orientation of the magnetic powder. After the magnetic layer 13 is formed, a back layer 14 is formed on the other main surface of the base layer 11. This completes the magnetic recording medium 10.

[0193] The ratio Hc2 / Hc1 can be set to a desired value by, for example, adjusting the strength of the magnetic field applied to the coating film of the magnetic layer-forming paint, the concentration of solids in the magnetic layer-forming paint, and the drying conditions (drying temperature and drying time) for the coating film of the magnetic layer-forming paint. The strength of the magnetic field applied to the coating film is preferably between two and three times the cohesive strength of the magnetic powder. To further increase the ratio Hc2 / Hc1, it is also preferable to magnetize the magnetic powder before the magnetic layer-forming paint enters an orientation device that magnetically orients the magnetic powder. Note that the methods for adjusting the ratio Hc2 / Hc1 may be used alone or in combination of two or more.

[0194] The resulting magnetic recording medium 10 is then rewound around a large diameter core and hardened. Finally, the magnetic recording medium 10 is calendered and then cut to a predetermined width (e.g., 1 / 2 inch width). This completes the desired long, thin magnetic recording medium 10.

[0195] (5) Recording and playback device

[0196] [Configuration of recording / playback device]

[0197] Next, with reference to FIG. 2, an example of the configuration of a recording / reproducing device 30 that performs recording and reproducing on the magnetic recording medium 10 having the above configuration will be described.

[0198] The recording / reproducing device 30 has a configuration that allows adjustment of the tension applied in the longitudinal direction of the magnetic recording medium 10. The recording / reproducing device 30 also has a configuration that allows a magnetic recording cartridge 10A to be loaded into it. Here, for ease of explanation, a case will be described in which the recording / reproducing device 30 has a configuration that allows one magnetic recording cartridge 10A to be loaded into it, but the recording / reproducing device 30 may also have a configuration that allows multiple magnetic recording cartridges 10A to be loaded into it. The recording and reproducing device 30 is preferably a timing servo type magnetic recording and reproducing device, and the magnetic recording medium of the present technology is suitable for use in a timing servo type magnetic recording and reproducing device.

[0199] The recording / reproducing device 30 is connected to information processing devices such as a server 41 and a personal computer (hereinafter referred to as "PC") 42 via a network 43, and is configured to be able to record data supplied from these information processing devices onto the magnetic recording cartridge 10A. The shortest recording wavelength of the recording / reproducing device 30 is preferably 100 nm or less, more preferably 75 nm or less, even more preferably 60 nm or less, and particularly preferably 50 nm or less.

[0200] As shown in FIG. 2, the recording / playback device includes a spindle 31, a reel 32 on the recording / playback device side, a spindle drive unit 33, a reel drive unit 34, a plurality of guide rollers 35, a head unit 36, a communication interface (hereinafter, I / F) 37, and a control unit 38.

[0201] The spindle 31 is configured so that a magnetic recording cartridge 10A can be attached thereto. The magnetic recording cartridge 10A conforms to the LTO (Linear Tape Open) standard, and rotatably accommodates a single reel 10C around which a magnetic recording medium 10 is wound in a cartridge case 10B. A V-shaped servo pattern is pre-recorded as a servo signal on the magnetic recording medium 10. The reel 32 is configured so that the leading end of the magnetic recording medium 10 pulled out from the magnetic recording cartridge 10A can be fixed. The present technology also provides a magnetic recording cartridge including a magnetic recording medium according to the present technology, in which the magnetic recording medium may be wound on a reel, for example.

[0202] The spindle drive device 33 is a device that rotates the spindle 31. The reel drive device 34 is a device that rotates the reel 32. When recording or reproducing data on the magnetic recording medium 10, the spindle drive device 33 and the reel drive device 34 rotate the spindle 31 and the reel 32, thereby running the magnetic recording medium 10. The guide roller 35 is a roller that guides the running of the magnetic recording medium 10.

[0203] The head unit 36 ​​includes a plurality of recording heads for recording data signals on the magnetic recording medium 10, a plurality of reproducing heads for reproducing the data signals recorded on the magnetic recording medium 10, and a plurality of servo heads for reproducing the servo signals recorded on the magnetic recording medium 10. A ring-type head can be used as the recording head, for example, but the type of recording head is not limited to this.

[0204] The communication I / F 37 is for communicating with information processing devices such as a server 41 and a PC 42, and is connected to a network 43.

[0205] The control device 38 controls the entire recording / reproducing device 30. For example, in response to a request from the information processing device, such as the server 41 or the PC 42, the control device 38 records a data signal supplied from the information processing device onto the magnetic recording medium 10 using the head unit 36. In addition, in response to a request from the information processing device, such as the server 41 or the PC 42, the control device 38 reproduces the data signal recorded on the magnetic recording medium 10 using the head unit 36, and supplies the reproduced data signal to the information processing device.

[0206] The control device 38 also detects changes in the width of the magnetic recording medium 10 based on the servo signals supplied from the head unit 36. Specifically, multiple V-shaped servo patterns are recorded as servo signals on the magnetic recording medium 10, and the head unit 36 ​​simultaneously reproduces two different servo patterns using two servo heads on the head unit 36, thereby obtaining respective servo signals. Using relative position information between the servo patterns and the head unit obtained from these servo signals, the position of the head unit 36 ​​is controlled to track the servo patterns. At the same time, distance information between the servo patterns can be obtained by comparing the two servo signal waveforms. By comparing the distance information between the servo patterns obtained during each measurement, the change in the distance between the servo patterns at each measurement can be obtained. By adding the distance information between the servo patterns obtained during servo pattern recording to this, the change in the width of the magnetic recording medium 10 can also be calculated. Based on the change in the distance between the servo patterns obtained as described above or the calculated change in the width of the magnetic recording medium 10, the control device 38 controls the rotational drive of the spindle drive device 33 and the reel drive device 34, and adjusts the tension in the longitudinal direction of the magnetic recording medium 10 so that the width of the magnetic recording medium 10 becomes a specified width or approximately a specified width. This makes it possible to suppress changes in the width of the magnetic recording medium 10.

[0207] [Recording / playback device operation]

[0208] Next, the operation of the recording / reproducing device 30 having the above configuration will be described.

[0209] First, the magnetic recording cartridge 10A is loaded into the recording / reproducing device 30, the leading end of the magnetic recording medium 10 is pulled out and transported to the reel 32 via a plurality of guide rollers 35 and a head unit 36, and the leading end of the magnetic recording medium 10 is attached to the reel 32.

[0210] Next, when an operating unit (not shown) is operated, the spindle drive device 33 and the reel drive device 34 are driven under the control of the control device 38, and the spindle 31 and the reel 32 are rotated in the same direction so that the magnetic recording medium 10 runs from the reel 10C toward the reel 32. As a result, the magnetic recording medium 10 is wound onto the reel 32, while the head unit 36 ​​records information onto the magnetic recording medium 10 or reproduces information recorded on the magnetic recording medium 10.

[0211] When rewinding the magnetic recording medium 10 onto the reel 10C, the spindle 31 and the reel 32 are rotated in the opposite direction to the above, causing the magnetic recording medium 10 to run from the reel 32 to the reel 10C. During this rewinding, the head unit 36 ​​also records information onto the magnetic recording medium 10 or reproduces information recorded on the magnetic recording medium 10.

[0212] (6) Variations

[0213] [Variation 1]

[0214] As shown in FIG. 3, the magnetic recording medium 10 may further include a barrier layer 15 disposed on at least one surface of the base layer 11. The barrier layer 15 is a layer for suppressing dimensional deformation of the base layer 11 due to environmental factors. For example, one cause of dimensional deformation is the hygroscopicity of the base layer 11, and the barrier layer 15 can reduce the rate at which moisture penetrates the base layer 11. The barrier layer 15 includes a metal or a metal oxide. Examples of metals that can be used include at least one of Al, Cu, Co, Mg, Si, Ti, V, Cr, Mn, Fe, Ni, Zn, Ga, Ge, Y, Zr, Mo, Ru, Pd, Ag, Ba, Pt, Au, and Ta. Examples of metal oxides that can be used include at least one of Al2O3, CuO, CoO, SiO2, Cr2O3, TiO2, Ta2O5, and ZrO2, as well as oxides of any of the above metals. Diamond-like carbon (DLC) or diamond can also be used.

[0215] The average thickness of the barrier layer 15 is preferably 20 nm or more and 1000 nm or less, more preferably 50 nm or more and 1000 nm or less. m However, the magnification of the TEM image is adjusted appropriately depending on the thickness of the barrier layer 15.

[0216] [Variation 2]

[0217] The magnetic recording medium 10 may be incorporated into a library device. That is, the present technology also provides a library device equipped with at least one magnetic recording medium 10. The library device has a configuration capable of adjusting the tension applied to the magnetic recording medium 10 in the longitudinal direction, and may be equipped with a plurality of the above-described recording / reproducing devices 30.

[0218] [Variation 3]

[0219] The magnetic recording medium 10 may be subjected to a servo signal writing process by a servo writer. The servo writer can maintain the width of the magnetic recording medium 10 constant or approximately constant by adjusting the tension in the longitudinal direction of the magnetic recording medium 10 during recording of the servo signal. In this case, the servo writer can include a detection device that detects the width of the magnetic recording medium 10. The servo writer can adjust the tension in the longitudinal direction of the magnetic recording medium 10 based on the detection result of the detection device.

[0220] 3. Second embodiment (1) One embodiment of a magnetic recording cartridge

[0221] [Cartridge configuration]

[0222] The present technology also provides a magnetic recording cartridge (also called a tape cartridge) including a magnetic recording medium according to the present technology. In the magnetic recording cartridge, the magnetic recording medium may be wound around a reel, for example. The magnetic recording cartridge may include, for example, a communication unit that communicates with a recording / reproducing device, a storage unit, and a control unit that stores information received from the recording / reproducing device via the communication unit in the storage unit, and reads information from the storage unit and transmits it to the recording / reproducing device via the communication unit in response to a request from the recording / reproducing device. The information may include adjustment information for adjusting the tension applied to the magnetic recording medium in the longitudinal direction.

[0223] An example of the configuration of a magnetic recording cartridge 10A equipped with a magnetic recording medium T having the above-described configuration will be described with reference to FIG.

[0224] 4 is an exploded perspective view showing an example of the configuration of a magnetic recording cartridge 10A. The magnetic recording cartridge 10A is a magnetic recording cartridge that complies with the LTO (Linear Tape-Open) standard, and includes a cartridge case 10B made up of a lower shell 212A and an upper shell 212B, a reel 10C around which a magnetic tape (a tape-like magnetic recording medium) T is wound, a reel lock 214 and a reel spring 215 for locking the rotation of the reel 10C, a spider 216 for unlocking the locked state of the reel 10C, a slide door 217 that straddles the lower shell 212A and the upper shell 212B and opens and closes a tape pull-out opening 212C provided in the cartridge case 10B, a door spring 218 that biases the slide door 217 to a closed position of the tape pull-out opening 212C, a write protect 219 for preventing accidental erasure, and a cartridge memory 211. The reel 10C is generally disk-shaped with an opening in the center, and is composed of a reel hub 213A made of a hard material such as plastic and a flange 213B. A leader tape LT is connected to one end of the magnetic tape T. A leader pin 220 is provided at the tip of the leader tape LT.

[0225] The cartridge memory 211 is provided near one corner of the magnetic recording cartridge 10A. When the magnetic recording cartridge 10A is loaded into the recording / reproducing device 80, the cartridge memory 211 faces a reader / writer (not shown) of the recording / reproducing device 80. The cartridge memory 211 communicates with the recording / reproducing device 30, specifically the reader / writer (not shown), using a wireless communication standard that complies with the LTO standard.

[0226] [Cartridge memory configuration]

[0227] An example of the configuration of the cartridge memory 211 will be described with reference to FIG.

[0228] 5 is a block diagram showing an example of the configuration of the cartridge memory 211. The cartridge memory 211 includes an antenna coil (communication unit) 331 that communicates with a reader / writer (not shown) using a specified communication standard, a rectification / power circuit 332 that generates power by using induced electromotive force from radio waves received by the antenna coil 331 and rectifying it, a clock circuit 333 that generates a clock from the radio waves received by the antenna coil 331 using the induced electromotive force, a detection / modulation circuit 334 that detects the radio waves received by the antenna coil 331 and modulates the signal to be transmitted by the antenna coil 331, a controller (control unit) 335 that is composed of logic circuits and the like for identifying and processing commands and data from the digital signal extracted from the detection / modulation circuit 334, and a memory (storage unit) 336 that stores information. The cartridge memory 211 also includes a capacitor 337 connected in parallel to the antenna coil 331, and the antenna coil 331 and capacitor 337 form a resonant circuit.

[0229] The memory 336 stores information related to the magnetic recording cartridge 10A. The memory 336 is a nonvolatile memory (NVM). The memory 336 preferably has a storage capacity of approximately 32 KB or more. For example, if the magnetic recording cartridge 10A conforms to the next-generation LTO format standard or later, the memory 336 has a storage capacity of approximately 32 KB.

[0230] The memory 336 has a first memory area 336A and a second memory area 336B. The first memory area 336A corresponds to the memory area of ​​a cartridge memory (hereinafter referred to as a "conventional cartridge memory") that conforms to the LTO standard prior to LTO8, and is an area for storing information that conforms to the LTO standard prior to LTO8. Information that conforms to the LTO standard prior to LTO8 includes, for example, manufacturing information (such as a unique number for the magnetic recording cartridge 10A), usage history (such as the number of times the tape has been pulled out (Thread Count)), etc.

[0231] The second memory area 336B corresponds to an extended memory area for the memory area of ​​a conventional cartridge memory. The second memory area 336B is an area for storing additional information. Here, additional information refers to information related to the magnetic recording cartridge 10A that is not specified in the LTO standard prior to LTO8. Examples of additional information include, but are not limited to, tension adjustment information, management ledger data, index information, and thumbnail information of videos stored on the magnetic tape T. The tension adjustment information includes the distance between adjacent servo bands (the distance between servo patterns recorded on adjacent servo bands) when data is recorded on the magnetic tape T. The distance between adjacent servo bands is an example of width-related information related to the width of the magnetic tape T. The distance between servo bands will be described in detail later. In the following description, the information stored in the first memory area 336A may be referred to as "first information," and the information stored in the second memory area 336B may be referred to as "second information."

[0232] The memory 336 may have multiple banks. In this case, some of the multiple banks may constitute the first storage area 336A, and the remaining banks may constitute the second storage area 336B. Specifically, for example, if the magnetic recording cartridge 10A conforms to the next-generation or later LTO format standard, the memory 336 may have two banks with a storage capacity of approximately 16 KB, and one of the two banks may constitute the first storage area 336A, and the other bank may constitute the second storage area 336B.

[0233] The antenna coil 331 induces an induced voltage by electromagnetic induction. The controller 335 communicates with the recording / reproducing device 80 using a specified communication standard via the antenna coil 331. Specifically, for example, mutual authentication, sending and receiving of commands, or data exchange is performed.

[0234] The controller 335 stores information received from the recording / reproducing device 80 via the antenna coil 331 in the memory 336. In response to a request from the recording / reproducing device 80, the controller 335 reads information from the memory 336 and transmits it to the recording / reproducing device 80 via the antenna coil 331.

[0235] (2) Modified magnetic recording cartridge

[0236] [Cartridge configuration]

[0237] In the above-described embodiment of the magnetic recording cartridge, the magnetic tape cartridge is described as a one-reel type cartridge, but the magnetic recording cartridge of the present technology may also be a two-reel type cartridge. That is, the magnetic recording cartridge of the present technology may have one or more (e.g., two) reels on which the magnetic tape is wound. Below, an example of a magnetic recording cartridge of the present technology having two reels will be described with reference to FIG. 6.

[0238] 6 is an exploded perspective view showing an example of the configuration of a two-reel type cartridge 421. Cartridge 421 includes an upper half 402 made of synthetic resin, a transparent window member 423 that fits into and is fixed to a window 402a opened in the top surface of upper half 402, a reel holder 422 that is fixed to the inside of upper half 402 and prevents reels 406 and 407 from floating up, a lower half 405 that corresponds to upper half 402, reels 406 and 407 that are stored in a space formed when upper half 402 and lower half 405 are combined, magnetic tape MT1 wound around reels 406 and 407, a front lid 409 that closes a front opening formed when upper half 402 and lower half 405 are combined, and a back lid 409A that protects magnetic tape MT1 exposed in this front opening.

[0239] The reel 406 includes a lower flange 406b having a cylindrical hub portion 406a in the center around which the magnetic tape MT1 is wound, an upper flange 406c having approximately the same size as the lower flange 406b, and a reel plate 411 sandwiched between the hub portion 406a and the upper flange 406c. The reel 407 has the same configuration as the reel 406.

[0240] The window member 423 is provided with mounting holes 423a at positions corresponding to the reels 406 and 407, respectively, for assembling reel holders 422, which are reel holding means for preventing these reels from floating up. The magnetic tape MT1 is the same as the magnetic tape T in the first embodiment.

[0241] The present technology can also employ the following configuration. [1] a magnetic layer containing magnetic powder; the magnetic layer contains first particles having electrical conductivity and second particles having a Mohs hardness of 7 or more, protrusions are formed on the surface of the magnetic layer side by the first particles and the second particles, A magnetic recording medium in which the average height (H2) of protrusions formed by the second particles is 7 nm or less, the magnetic recording medium contains a fatty acid, and the extraction rate of the fatty acid, as defined by the following formula, is 45% or more. Extraction rate of fatty acids (%) = [5-minute extraction amount of fatty acids (mg / m 2 ) / Total fatty acid extraction amount (mg / m 2 )] x 100 [2] 5-minute extraction amount of fatty acids (mg / m 2 ) is 3.0 mg / m 2 The magnetic recording medium according to [1] above. [3] Total fatty acid extraction (mg / m 2 ) is 5.0 mg / m 2 The magnetic recording medium according to [1] or [2] above. [4] The magnetic recording medium according to any one of [1] to [3], wherein the fatty acid is stearic acid. [5] The magnetic recording medium according to any one of [1] to [4], further comprising a fatty acid ester, wherein the extraction rate of the fatty acid ester defined by the following formula is 60% or more. Extraction rate of fatty acid ester (%) = [5-minute extraction amount of fatty acid ester (mg / m 2 ) / Total fatty acid ester extract (mg / m 2 )] x 100 [6] 5-minute extraction amount of fatty acid esters (mg / m 2 ) is 10.0 mg / m 2 The magnetic recording medium according to [5] above. [7] Total fatty acid ester extractables (mg / m 2 ) is 12.0 mg / m 2 The magnetic recording medium according to [5] or [6] above. [8] The magnetic recording medium according to any one of [5] to [7], wherein the fatty acid ester is butyl stearate. [9] The magnetic recording medium according to any one of [1] to [8], wherein the average thickness of the magnetic layer is 0.08 μm or less.

[10] The magnetic recording medium according to any one of [1] to [9], further comprising a non-magnetic layer.

[11] The magnetic recording medium according to

[10] , wherein the average thickness of the non-magnetic layer is 1.2 μm or less.

[12] The magnetic recording medium according to any one of [1] to

[11] , which has an average thickness (average total thickness) of 5.7 μm or less.

[13] The magnetic recording medium according to any one of [1] to

[12] , wherein the surface of the magnetic powder is coated with a coating agent.

[14] The magnetic recording medium according to

[13] , wherein the coating agent is an organic acid.

[15] The magnetic recording medium according to any one of [1] to

[14] , wherein the second particles are inorganic particles.

[16] The magnetic recording medium according to any one of [1] to

[15] , wherein the second particles are alumina particles.

[17] A magnetic recording cartridge in which the magnetic recording medium according to any one of [1] to

[16] is housed in a case in a state where it is wound around a reel.

[0242] 4. Working Example

[0243] Hereinafter, the present technology will be specifically explained using examples, but the present technology is not limited to these examples.

[0244] In this example, the average height of the protrusions formed by the second particles (referred to as AFM_protrusion average height in Table 1), the extraction rate of fatty acids, the 5-minute extraction amount of fatty acids, the total extraction amount of fatty acids, the extraction rate of fatty acid esters, the 5-minute extraction amount of fatty acid esters, the total extraction amount of fatty acid esters, the average thickness of the magnetic tape (average total thickness) t T , the average thickness of the magnetic layer t m The average thickness of the non-magnetic layer (underlayer), the average thickness of the base layer, the average thickness of the back layer, deposits, and output degradation were determined by the measurement method described in the above embodiment.

[0245] [Example 1] (Preparation process of paint for forming magnetic layer) The magnetic layer-forming paint was prepared as follows. First, a first composition having the following formulation was kneaded using an extruder. Next, the kneaded first composition and a second composition having the following formulation were added to a stirring tank equipped with a disperser and premixed. Subsequently, further sand mill mixing was performed and filtering was carried out to prepare the magnetic layer-forming paint.

[0246] (First composition) Magnetic powder (hexagonal ferrite with M-type structure, composition: Ba-Ferrite, shape: plate-shaped hexagonal particles, average particle volume: 1600 nm 3 ):100 parts by mass Vinyl chloride resin (cyclohexanone solution 30% by mass): 46 parts by mass (Degree of polymerization: 300, Mn=10,000, contains polar groups OSO3K=0.07 mmol / g and secondary OH=0.3 mmol / g.) Aluminum oxide powder: 7.5 parts by mass (α-Al2O3, average particle size 50 nm, manufactured by Sumitomo Chemical Co., Ltd., product name: HIT100, Mohs hardness: 9) Carbon black: 2.0 parts by mass (Average particle size 70 nm, manufactured by Tokai Carbon Co., Ltd., product name: Seest TA)

[0247] (Second composition) Vinyl chloride resin: 1.6 parts by mass (Cyclohexanone solution 30% by mass resin) n-Butyl stearate: 2 parts by mass Methyl ethyl ketone: 121.3 parts by mass Toluene: 121.3 parts by mass Cyclohexanone: 60.7 parts by mass

[0248] Finally, 2 parts by mass of polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation) and 2 parts by mass of stearic acid were added as curing agents to the magnetic layer-forming coating material prepared as described above. The P / B ratio of the magnetic layer, which refers to the ratio of magnetic powder to adhesive (binder), was 5.0. The P / B ratios for each example are shown in Table 1 below.

[0249] (Preparation process of paint for forming base layer) The paint for forming a primer layer was prepared as follows. First, the third composition having the following composition was kneaded using an extruder. Next, the kneaded third composition and the fourth composition having the following composition, excluding stearic acid and butyl stearate, were added to a stirring tank equipped with a disperser and premixed. Next, further sand mill mixing was performed, stearic acid and butyl stearate were added, and the mixture was filtered to prepare the paint for forming a primer layer.

[0250] (Third composition) Acicular iron oxide powder: 100 parts by weight (α-Fe2O3, average major axis length 0.15μm) Vinyl chloride resin: 55.6 parts by mass (Resin solution: 30% resin by mass, 70% cyclohexanone by mass) Citric acid: 5 parts by mass Carbon black: 10 parts by mass (Average particle size 20nm)

[0251] (4th composition) Polyurethane resin UR8200 (manufactured by Toyobo): 18.5 parts by weight Stearic acid: 2 parts by weight Butyl stearate: 2 parts by weight Methyl ethyl ketone: 75 parts by weight Toluene: 75 parts by weight Cyclohexanone: 35 parts by weight

[0252] Finally, 2 parts by mass of polyisocyanate (trade name: Coronate L, manufactured by Tosoh Corporation) as a curing agent and 2 parts by mass of stearic acid were added to the coating material for forming the undercoat layer prepared as described above.

[0253] (Preparation process of paint for forming back layer) The coating material for forming a back layer was prepared as follows: The following raw materials were mixed in a stirring tank equipped with a disperser, and the mixture was filtered to prepare the coating material for forming a back layer. Carbon black (manufactured by Asahi Corporation, product name: #80): 100 parts by mass Polyester polyurethane: 100 parts by mass (Nippon Polyurethane Co., Ltd., product name: N-2304) Methyl ethyl ketone: 500 parts by mass Toluene: 400 parts by mass Cyclohexanone: 100 parts by mass Polyisocyanate (product name: Coronate L, manufactured by Tosoh Corporation): 10 parts by mass

[0254] (Film forming process) Using the coating material prepared as described above, a magnetic tape was prepared as follows.

[0255] First, a PEN film (base film) having a long shape and an average thickness of 4.0 μm was prepared as a support for the base layer of the magnetic tape.Next, a base layer forming paint was applied to one main surface of the PEN film and dried, thereby forming a base layer on one main surface of the PEN film so that the average thickness of the final product would be 1.05 μm.Next, a magnetic layer forming paint was applied to the base layer and dried, thereby forming a magnetic layer on the base layer so that the average thickness of the final product would be 0.08 μm.

[0256] Next, a back layer-forming coating material was applied to the other main surface of the PEN film on which the undercoat layer and magnetic layer were formed, and then dried to form a back layer with an average thickness of 0.50 μm in the final product.The PEN film on which the undercoat layer, magnetic layer, and back layer were formed was then subjected to a curing treatment.Then, a calendering treatment was performed to smooth the surface of the magnetic layer.

[0257] (Cutting process) The magnetic tape obtained as described above was cut into a width of 1 / 2 inch (12.65 mm), thereby obtaining a long magnetic tape.

[0258] The 1 / 2-inch-wide magnetic tape was wound around a reel provided inside a cartridge case to obtain a magnetic recording cartridge. A servo signal was recorded on the magnetic tape using a servo track writer. The servo signal consisted of a series of V-shaped magnetic patterns, and the magnetic patterns were pre-recorded in two or more rows parallel to the longitudinal direction at known intervals (hereinafter referred to as "the known intervals between pre-recorded magnetic pattern rows").

[0259] The magnetic tape obtained had an extraction rate of 53% of stearic acid and a 5-minute extraction amount of stearic acid of 4.81 mg / m 2 , total extractable amount of stearic acid is 9.13mg / m 2 The extraction rate of butyl stearate was 68%, and the 5-minute extractable amount of butyl stearate was 13.30 mg / m 2 , total extractable amount of butyl stearate is 19.42 mg / m 2 In addition, the average height (H2) of the protrusions formed by α-Al2O3 was 5.3 nm, and the average thickness (average total thickness) of the magnetic tape was t T is 5.56 μm, and the average thickness of the magnetic layer t m The average thickness of the non-magnetic layer (underlayer) was 1.13 μm, the average thickness of the base layer was 4.0 μm, and the average thickness of the back layer was 0.36 μm. In addition, there was little adhesion to the magnetic head, and no deterioration in output occurred.

[0260] [Example 2] A magnetic tape was obtained in the same manner as in Example 1, except that phenylphosphonic acid was used as the organic acid. The extraction rate of stearic acid was 45%, and the 5-minute extraction amount of stearic acid was 4.47 mg / m 2 , total extractable amount of stearic acid is 9.93mg / m 2 The extraction rate of butyl stearate was 61%, and the 5-minute extractable amount of butyl stearate was 12.06 mg / m 2 , total extractable amount of butyl stearate is 19.80mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 5.4 nm. There was also little adhesion to the magnetic head, and no output degradation occurred.

[0261] [Example 3] A magnetic tape was obtained in the same manner as in Example 1, except that the amount of stearic acid added was increased. The extraction rate of stearic acid was 50%, and the 5-minute extraction amount of stearic acid was 6.15 mg / m 2 , the total extractable amount of stearic acid is 12.32 mg / m 2 The extraction rate of butyl stearate was 67%, and the 5-minute extractable amount of butyl stearate was 13.37 mg / m 2 , total extractable amount of butyl stearate is 19.84 mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 5.3 nm. There was also little adhesion to the magnetic head, and no output degradation occurred.

[0262] [Example 4] A magnetic tape was obtained in the same manner as in Example 1, except that the magnetic layer thickness was reduced. The extraction rate of stearic acid was 59%, and the 5-minute extraction amount of stearic acid was 5.05 mg / m 2 , total extractable amount of stearic acid is 8.61mg / m 2 The extraction rate of butyl stearate was 69%, and the 5-minute extractable amount of butyl stearate was 12.48 mg / m 2 , total extractable amount of butyl stearate is 17.96 mg / m 2The average height (H2) of the protrusions formed by α-Al2O3 was 5.4 nm. There was also little adhesion to the magnetic head, and no output degradation occurred.

[0263] [Example 5] A magnetic tape was obtained in the same manner as in Example 1, except that the amount of hardener in the magnetic layer was reduced. The extraction rate of stearic acid was 49%, and the 5-minute extraction amount of stearic acid was 4.54 mg / m 2 , total extractable amount of stearic acid is 9.29 mg / m 2 The extraction rate of butyl stearate was 65%, and the 5-minute extractable amount of butyl stearate was 12.21 mg / m 2 , total extractable amount of butyl stearate is 18.86 mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 5.4 nm. There was also little adhesion to the magnetic head, and no output degradation occurred.

[0264] [Example 6] A magnetic tape was obtained in the same manner as in Example 1, except that the amount of citric acid added to the paint for forming the undercoat layer was increased. The extraction rate of stearic acid was 56%, and the 5-minute extraction amount of stearic acid was 5.25 mg / m 2 , total extractable amount of stearic acid is 9.32mg / m 2 The extraction rate of butyl stearate was 64%, and the 5-minute extractable amount of butyl stearate was 12.41 mg / m 2 , total extractable amount of butyl stearate is 19.29 mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 4.8 nm. There was also little adhesion to the magnetic head, and no output degradation occurred.

[0265] [Example 7] A magnetic tape was obtained in the same manner as in Example 1, except that the type of base film was changed to a PET film. The extraction rate of stearic acid was 51%, and the 5-minute extractable amount of stearic acid was 4.97 mg / m 2, total extractable amount of stearic acid is 9.69mg / m 2 The extraction rate of butyl stearate was 66%, and the 5-minute extractable amount of butyl stearate was 13.47 mg / m 2 , total extractable amount of butyl stearate is 20.51 mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 4.6 nm. There was also little adhesion to the magnetic head, and no output degradation occurred.

[0266] [Example 8] A magnetic tape was obtained in the same manner as in Example 1, except that the calendering temperature was lowered. The extraction rate of stearic acid was 53%, and the 5-minute extraction amount of stearic acid was 5.25 mg / m 2 , total extractable amount of stearic acid is 9.96mg / m 2 The extraction rate of butyl stearate was 72%, and the 5-minute extractable amount of butyl stearate was 14.72 mg / m 2 , total extractable amount of butyl stearate is 20.47mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 6.0 nm. There was also little adhesion to the magnetic head, and no output degradation occurred.

[0267] [Example 9] A magnetic tape was obtained in the same manner as in Example 1, except that the calendering temperature was increased. The extraction rate of stearic acid was 51%, and the 5-minute extraction amount of stearic acid was 4.72 mg / m 2 , total extractable amount of stearic acid is 9.19mg / m 2 The extraction rate of butyl stearate was 71%, and the 5-minute extractable amount of butyl stearate was 13.61 mg / m 2 , total extractable amount of butyl stearate is 19.29 mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 5.3 nm. There was also little adhesion to the magnetic head, and no output degradation occurred.

[0268] [Example 10] Example 1 is a magnetic powder volume of 1200 nm 3 A magnetic tape was obtained in the same manner as in Example 1, except that the extraction rate of stearic acid was 48%, and the 5-minute extractable amount of stearic acid was 4.70 mg / m 2 , total extractable amount of stearic acid is 9.75mg / m 2 The extraction rate of butyl stearate was 64%, and the 5-minute extractable amount of butyl stearate was 12.99 mg / m 2 , total extractable amount of butyl stearate is 20.29 mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 5.1 nm. There was also little adhesion to the magnetic head, and no output degradation occurred.

[0269] [Example 11] Example 1 is a magnetic powder volume of 2500 nm 3 A magnetic tape was obtained in the same manner as in Example 1, except that the extraction rate of stearic acid was 54%, and the 5-minute extractable amount of stearic acid was 4.85 mg / m 2 , total extractable amount of stearic acid is 9.06mg / m 2 The extraction rate of butyl stearate was 67%, and the 5-minute extractable amount of butyl stearate was 13.05 mg / m 2 , total extractable amount of butyl stearate is 19.55mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 4.7 nm. There was also little adhesion to the magnetic head, and no output degradation occurred.

[0270] [Example 12] A magnetic tape was obtained in the same manner as in Example 1, except that the P / B ratio of the underlayer was changed. The extraction rate of stearic acid was 58%, and the 5-minute extraction amount of stearic acid was 4.53 mg / m 2 , total extractable amount of stearic acid is 7.76mg / m 2 The extraction rate of butyl stearate was 79%, and the 5-minute extractable amount of butyl stearate was 10.81 mg / m 2, total extractable amount of butyl stearate is 13.67mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 5.8 nm. There was also little adhesion to the magnetic head, and no output degradation occurred.

[0271] [Example 13] A magnetic tape was obtained in the same manner as in Example 1, except that the P / B ratio of the underlayer was changed and phenylphosphonic acid was used as the organic acid. The extraction rate of stearic acid was 55%, and the 5-minute extraction amount of stearic acid was 3.86 mg / m 2 , total extractable amount of stearic acid is 7.06mg / m 2 The extraction rate of butyl stearate was 77%, and the 5-minute extractable amount of butyl stearate was 11.18 mg / m 2 , total extractable amount of butyl stearate is 14.48mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 5.8 nm. There was also little adhesion to the magnetic head, and no output degradation occurred.

[0272] [Comparative Example 1] A magnetic tape was obtained in the same manner as in Example 1, except that the amount of organic acid added was smaller. The extraction rate of stearic acid was 41%, and the 5-minute extractable amount of stearic acid was 3.49 mg / m 2 , total extractable amount of stearic acid is 8.48mg / m 2 The extraction rate of butyl stearate was 64%, and the 5-minute extractable amount of butyl stearate was 12.55 mg / m 2 , total extractable amount of butyl stearate is 19.50 mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 5.3 nm. There was significant output degradation and a lot of head damage.

[0273] Comparative Example 2 A magnetic tape was obtained in the same manner as in Comparative Example 1, except that α-Al2O3 with a particle size of 80 nm (HIT-82) was used and the amount of butyl stearate was reduced. The extraction rate of stearic acid was 41%, and the 5-minute extraction amount of stearic acid was 2.44 mg / m 2 , total extractable amount of stearic acid is 5.90mg / m 2 The extraction rate of butyl stearate was 59%, and the 5-minute extractable amount of butyl stearate was 6.74 mg / m 2 , total extractable amount of butyl stearate is 11.35mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 5.2 nm. A large amount of material adhered to the magnetic head.

[0274] Comparative Example 3 The magnetic powder volume of Comparative Example 1 is 2500 nm 3 A magnetic tape was obtained in the same manner as in Comparative Example 1, except that the extraction rate of stearic acid was 38%, and the 5-minute extractable amount of stearic acid was 2.72 mg / m 2 , total extractable amount of stearic acid is 7.17mg / m 2 The extraction rate of butyl stearate was 51%, and the 5-minute extractable amount of butyl stearate was 5.73 mg / m 2 , total extractable amount of butyl stearate is 11.20 mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 5.1 nm. There was significant output degradation and a lot of head damage.

[0275] Comparative Example 4 The magnetic tape was obtained in the same manner as in Example 1, except that the average height (H2) of the protrusions formed by α-Al2O3 was greater than 7 nm, and the total amount of stearic acid extracted and the 5-minute amount of stearic acid extracted were small. The extraction rate of stearic acid was 51%, and the 5-minute amount of stearic acid extracted was 1.51 mg / m 2 , total extractable amount of stearic acid is 2.97mg / m 2 The extraction rate of butyl stearate was 91%, and the 5-minute extractable amount of butyl stearate was 23.87 mg / m 2, total extractable amount of butyl stearate is 26.29 mg / m 2 The average height (H2) of the protrusions formed by α-Al2O3 was 8.2 nm. There was significant output degradation and a lot of head damage.

[0276] Table 1 shows the configurations and evaluation results of the magnetic tapes of Examples 1 to 13 and Comparative Examples 1 to 4.

[0277] [Table 1]

[0278] The symbols in Table 1 represent the following measured values. t T : Average thickness of magnetic tape (average total thickness) (unit: μm) t m : Average thickness of magnetic layer (unit: nm) t b : Average thickness of back layer (unit: μm)

[0279] The results shown in Table 1 reveal the following:

[0280] In all of the magnetic tapes of Examples 1 to 13, the average height (H2) of the protrusions formed by the secondary particles was 7 nm or less, the extraction rate of stearic acid, a fatty acid, was 45% or more, there was little adhesion to the magnetic head, and no output degradation occurred.

[0281] Comparing Example 1 and Comparative Example 1, the magnetic tape of Example 1 had an average height (H2) of the protrusions formed by the second particles of 7 nm or less, an extraction rate of stearic acid of 45% or more, little adhesion to the magnetic head, and no output degradation. On the other hand, the magnetic tape of Comparative Example 1 had an extraction rate of stearic acid of less than 45%, and the degree of output degradation was greater than that of Example 1.

[0282] Furthermore, when comparing Comparative Example 1 and Comparative Example 2, the magnetic tape of Comparative Example 2 had an extraction rate of butyl stearate of less than 50%, and a large amount of material adhered to the magnetic head.

[0283] Furthermore, when comparing Comparative Example 1 and Comparative Example 3, the magnetic tape of Comparative Example 3 had an extraction rate of butyl stearate of less than 60%, which resulted in a large amount of material adhering to the magnetic head and a large degree of output degradation.

[0284] Furthermore, when comparing Example 1 with Comparative Example 4, the magnetic tape of Comparative Example 4 had a stearic acid extraction rate of 45% or more, but the height of the protrusions formed by the alumina corresponding to the secondary particles exceeded 7 nm, and the degree of output degradation was significant.

[0285] Although the embodiments and examples of the present technology have been specifically described above, the present technology is not limited to the above-described embodiments and examples, and various modifications based on the technical ideas of the present technology are possible.

[0286] For example, the configurations, methods, steps, shapes, materials, and numerical values, etc., given in the above-described embodiments and examples are merely examples, and different configurations, methods, steps, shapes, materials, and numerical values, etc., may be used as necessary. Furthermore, the chemical formulas of compounds, etc., are representative, and are not limited to the valences, etc., given as long as they are general names of the same compounds.

[0287] Furthermore, the configurations, methods, processes, shapes, materials, numerical values, and the like of the above-described embodiments and examples can be combined with each other without departing from the spirit of the present technology.

[0288] Furthermore, in this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit of a numerical range in one stage may be replaced with the upper or lower limit of a numerical range in another stage. Unless otherwise specified, the materials exemplified in this specification can be used alone or in combination of two or more types. [Explanation of symbols]

[0289] 10 Magnetic recording media 11 Base Layer 12 Base layer 13 Magnetic layer 14 Back layer

Claims

1. a magnetic layer containing magnetic powder; the magnetic layer contains first particles having electrical conductivity and second particles having a Mohs hardness of 7 or more, protrusions are formed on the surface of the magnetic layer side by the first particles and the second particles, the average height (H2) of protrusions formed by the second particles is 7 nm or less, the second particles contain fatty acids, and the extraction rate of the fatty acids defined by the following formula is 45% or more, A magnetic recording medium further comprising a fatty acid ester, wherein the extraction rate of the fatty acid ester defined by the following formula is 60% or more. Extraction rate of fatty acids (%) = [5-minute extraction amount of fatty acids (mg / m ２ ) / Total fatty acid extraction amount (mg / m ２ ) × 100 Extraction rate of fatty acid ester (%) = [5-minute extraction amount of fatty acid ester (mg / m ２ ) / Total Extraction Amount of Fatty Acid Esters (mg / m ２ ) × 100

2. 5-minute extraction amount of fatty acids (mg / m ２ ) is 3.0 mg / m ２ 2. The magnetic recording medium according to claim 1, wherein:

3. Total fatty acid extraction amount (mg / m ２ ) is 5.0 mg / m ２ 2. The magnetic recording medium according to claim 1, wherein:

4. 2. The magnetic recording medium according to claim 1, wherein the fatty acid is stearic acid.

5. 5-minute extraction amount of fatty acid ester (mg / m ２ ) is 10.0 mg / m ２ 2. The magnetic recording medium according to claim 1, wherein:

6. Total fatty acid ester extractables (mg / m ２ ) is 12.0 mg / m ２ 2. The magnetic recording medium according to claim 1, wherein:

7. 2. The magnetic recording medium according to claim 1, wherein the fatty acid ester is butyl stearate.

8. 2. The magnetic recording medium according to claim 1, wherein the average thickness of the magnetic layer is 0.08 [mu]m or less.

9. The magnetic recording medium according to claim 1 , further comprising a non-magnetic layer.

10. 10. The magnetic recording medium according to claim 9, wherein the average thickness of the non-magnetic layer is 1.2 [mu]m or less.

11. 2. The magnetic recording medium according to claim 1, wherein the average thickness (average total thickness) is 5.7 [mu]m or less.

12. 2. The magnetic recording medium according to claim 1, wherein the surface of the magnetic powder is coated with a coating agent.

13. The magnetic recording medium according to claim 12, wherein the coating agent is an organic acid.

14. The magnetic recording medium according to claim 1 , wherein the second particles are inorganic particles.

15. 2. The magnetic recording medium according to claim 1, wherein the second particles are alumina particles.

16. 10. A magnetic recording cartridge, comprising the magnetic recording medium according to claim 1 wound around a reel and housed in a case.

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